2025-06-22 05:51来源:本站
实验涉及共有20个成年雄性埃及水果蝙蝠(Rousettus aegyptiacus;重量,约150-190 g),其中八个收集了神经数据。蝙蝠的分布如下:行为,五个蝙蝠(社会组1),五个蝙蝠(社会组2),两个蝙蝠(对象实验);和神经记录,将五个蝙蝠植入了四个四个微型训练(三个与社会组1和2一起觅食;两个参与对象实验的涉及),另外三个蝙蝠则与微型显微镜(与社交组1和2一起觅食)。实验包括10-20个每日觅食会话,其中涉及一组5-7个蝙蝠(社会群体加一两个植入动物;主要电生理数据集的组成图2a图2a)或一组三个蝙蝠和一个移动对象。所有动物均被安置在湿度和温度控制的房间中。在实验开始和实验时期之间,将非植入动物饲养在公共实验室男性菌落中。在实验期间,将动物与其他蝙蝠一起安置在单独的住房室中。非植入动物的动物被安置在大笼子里,每个社会群体都有一个。植入的动物最初是单一饲养的,随后在手术中恢复后,与其他蝙蝠共同居住在大笼子中。在12 h – 12 h的反向光周期(灯光下方 - 灯光上,07:00–19:00)保持住房室中的灯光。所有实验均在清醒时间(黑暗周期)的一天中的同一时间进行。所有实验程序均由加州大学伯克利分校的机构动物护理和使用委员会批准。
所有实验均在具有均匀照明(亮度5 lux)的高精度照明控制48中进行声学,电气和射频屏蔽室(5.6 m×5.2 m×2.5 m)进行,使动物可以使用两种近端(触摸,olfaction)以及远处(视觉,听觉)的感觉。为了最大程度地减少外部的声音混响和潮湿的噪音,飞行室的天花板和墙壁被声音泡沫覆盖。另一层吸收的黑色毡用于保护声泡沫免受蝙蝠的损坏,同时保持预期的声学环境。飞行室的地板还覆盖着相同的吸收黑色毡。使用商业RTL(Ciholas)的修改版本记录所有动物的3D空间位置。该系统由移动标签(DWTAG100)组成,这些标签由16个静态锚(DWETH101)以100 Hz采样率识别并定位,提供了系统的参考位置(锚固的布置在扩展数据中显示了图1B)。通过超宽带脉冲传达的锚定和标签。一个附加的锚(自定义DWETH101)用于记录外部同步信号(见下文)。标签由轻巧(〜2.9 g)的收发器和脂肪电池制成,安装在定制的项圈上(总计约15克)。标签中包括16位三轴加速度计,可以在100 Hz时提供加速度数据。该系统通过用户数据报协议(UDP)与位于房间外部的计算机通信,并通过在Ubuntu v.18.04 Bionic上运行的基于Web的用户界面进行配置和操作。使用Python v.3.9中的自定义书面脚本记录并保存数据。通过与RTL同时跟踪一个或两个蝙蝠,以及一个高度精确的基于摄像头的系统(运动分析24,25,48),通过同时跟踪一个或两个蝙蝠,在实验的一部分上测量了系统的空间分辨率(24,25,48) 并在10–20厘米的范围内(扩展数据图1C,D)。对于电生理学和成像,集体空间实验由两种类型之一组成,每种实验与五只蝙蝠(社会组1或2)的单独基线组永久相关,并且仅与食物源(碗或饲养者,请参见下文)不同。从手术中恢复后,将植入的蝙蝠添加到基线组中。在小组会议之前,所有蝙蝠都受到轻度限制(> 85%的基线体重),即使在其全部重量时也经常积极参加觅食实验,这表明食物不是积极参与的主要驱动力。在碗觅食的情况下(社交组1),一碗或一盘香蕉块位于房间的中心附近,离地面约0.5 m,蝙蝠可以自发地从中收集香蕉块。碗通常装满60-100克香蕉,偶尔在会议中间得到补充。对于饲养者磨损(社会组2),如前所述24,25,48所述,在房间一端放置了四个自动化馈线。当蝙蝠降落在喂食平台上并打断奖励端口前面的红外光束传感器时,会触发奖励。馈线全部由Arduino(UNO Rev3)和Adafruit Motorshield(1438; Adafruit)独立控制,并与实验室外的一台计算机连接。为了鼓励蝙蝠在收集食物后离开喂食器,我们在触发蝙蝠后禁用了喂食器。下一个进料可能是由不同的蝙蝠降落在同一喂食器上或同一只蝙蝠的情况下触发的,在离开进料器并返回后(越过距喂食器0.7 m的虚拟障碍物)。我们还进行了涉及一个与上述有两个主要区别的动态对象的实验:(1) 他们涉及三个蝙蝠从一个单一喂食器(其中两个用四极微训练植入);(2)他们涉及一个物体(一个泡沫塑料球,直径20厘米;扩展数据图8a),可以使用索道系统和皮带轮从房间外移动。物体在蝙蝠最常占据的两个位置之间移动:一个靠近休息地点(Perch),另一个靠近进料器。为了创建动态上下文,在这两个位置之间每10-15分钟移动球,并且有时会出现一些错误的开始和突然的运动。蝙蝠零星地降落在球上,并经常用翅膀的尖端将其碰到降落。每个蝙蝠(以及对象的)的位置和身份通过RTL不断监测,与控制进料器的自定义MATLAB脚本接口。觅食时间持续了60至150分钟,并从从飞行室入口附近的一个小笼子中释放出来的所有非植入蝙蝠开始。当植入蝙蝠参加实验时,小组觅食会议的两侧是两个休息时间,持续5-10分钟,其中将植入的蝙蝠保持在一个小笼子(25 cm×32 cm×46 cm)中,在不透明的箱子内(40 cm×46 cm×46 cm×46 cm×46 cm×65 cm×65 cm)。释放非植入蝙蝠后,植入的蝙蝠在觅食会开始时立即从小笼子中释放出来。在小组行为和休息课程中都记录了神经活动。Master-9设备(A.M.P.I.)生成的周期性时钟脉冲用于创建一个定时签名,该定时签名用作所有记录系统(跟踪,神经记录和音频,请参见下文)。
进行电生理植入物的手术程序类似于先前针对埃及水果BATS23,24,49的外科手术。每只蝙蝠的右半球植入了轻巧的四个四极微型训练(Harlan 4 Drive; neuralynx)。四极由四链铂 - iridium电线(直径为17.8 µm,HML绝缘)制成,并如前所述组装24。将四个四极管中的每一个都加载到安装在微训练中的聚酰胺管的望远镜组件中,并且可以单独移动(〜5 mm行进)。在手术前的第二天,将每个四极管的尖端扁平并用金镀金溶液(NeuralyNX)铺板,以将单个电线的阻抗降低至0.2-0.5MΩ。在手术当天,使用氯胺酮,右美托咪定和咪达唑仑的可注射鸡尾酒诱导麻醉。然后将蝙蝠放置在立体定位设备(942型; KOPF)中,并通过注射(每小时大约每小时一次)的麻醉鸡尾酒鸡尾酒,米唑仑和芬太尼的麻醉鸡尾酒来维持麻醉。通过测试脚趾捏反射并测量蝙蝠的呼吸速率,不断监测麻醉的深度。使用直肠温度探针测量蝙蝠的体温,并通过调节的加热垫保持大约35°C。在验证有效麻醉后,将颅骨暴露,清洁和周围的皮肤和组织缩回。在手术期间,在放置微训练之前,对头骨进行评分以提高粘附和机械稳定性。骨螺钉(19010-00; FST),上面插入了一条短的不锈钢线(0.008英寸,PFA涂层; A-M系统)焊接到螺钉头上,插入额板的头骨中,并用作地面。另外四个骨螺钉(M1.59×2毫米,不锈钢) 被放入头骨中以进行植入物的机械稳定性。在右半球上方的头骨上,在横向窦的前面7毫米的横向鼻窦和小脑的后部和小脑和中线侧面3.2 mm的3.2毫米之间,在右半球上方的头骨上进行了2 mm的圆形颅骨切开术。颅骨切开术被生物相容性的弹性体(Kwik-Sil; World Precision Instruments)覆盖,直到植入微晶体为止。头骨和螺钉的底部被薄薄的骨水泥(C&B metabond)覆盖。接下来,在从颅骨切开术中去除kwik-sil并进行了尿道切开术后,微型训练缓慢地降低,并用完全缩回的四极管降低,以产生紧密的密封,其余的裸露大脑被Kwik-sil覆盖。施用牙科丙烯酸将微晶固定到螺钉和头骨上。从微旋翼连接到地面螺钉的电线,并用牙科丙烯酸连接到电线。所有四个四极管最初均位于手术结束时皮质表面以下约800 µm处。最后,在手术后将止痛药(metacam; Boehringer Ingelheim)给予蝙蝠。镇痛药(3天)和抗生素(7天)每天在手术后每天服用,直到完全恢复。
手术后,在1-2周的时间内降低了四极管的较小的每日增量,朝着背部海马的锥体层(CA1和CA2)降低。锥体细胞层是通过局部场电位中的高频波纹的存在,与瞬时(50-100毫秒)增加的多单位活性相关的。在蝙蝠在一个小织物袋中盘旋时,进行了四极管的所有调整:每天通过将蝙蝠的微旋转与有线记录系统(数字lynx; neuralynx)连接到实验开始和完成后,通过将蝙蝠的微旋转连接到有线记录系统(数字lynx; neuralynx)来监测。在每个记录会话结束时,通常将一个或多个四极管移动(20–160 µm),以在第二天从不同的神经元进行采样,同时确保组织稳定组织的最大时间。后来对四极管位置进行组织学验证(见下文)。为了记录自由飞行蝙蝠的神经活动,我们使用了无线神经数据遗传系统(神经库; Mouselog16,垂直版本,Deuteron Technologies)。该记录仪与定制设计的3D打印外壳一起放置,RTLS标签和两个Lipo电池(一个用于记录器,一个用于RTLS标签;最小持续时间,150分钟),并连接到每个录制开始时的微型电源界面电源板。整个系统重约15-17 g。我们的实验中使用的植入蝙蝠的重量超过150 g,并且在配备神经胶凝物的同时可能会正常飞行,这是使用无线记录系统的先前实验所预期的。放大了来自四个四四极管(16个通道)的电信号(200×),带通滤波(1-7,000 Hz),以29.34 kHz的频率连续采样,并存储在记录器上的SD卡存储器上, 电压分辨率为3.3 µV。神经遗嘱者和静态收发器之间的无线通信确保了正确的同步,并允许通过软件(Deuteron Technologies)进行基本的监视和配置。在录制会话结束时,从记录器中提取数据并保存。如先前所述9,24进行了尖峰排序。简而言之,对记录的电压轨迹进行过滤(600-6,000 Hz),并通过阈值(3 S.D.)检测到推定的尖峰。推定的尖峰波形(32个样本,第八个样品的峰值)用作群集排序软件(Spikesort 3D,NeuralyNX)的输入。尖峰振幅和能量被用作手动分类的功能。不稳定的单元,具有尖峰振幅的可见漂移,来自仔细评估整个疗程电压痕迹的四型单元,这些单元来自局部野外电势并未在局部野外电势中表现出涟漪。仅对于CA1和CA2之间的比较(参考文献50)(扩展数据表1),使用来自啮齿动物海马和BATS的海马34,51所采用的类似标准,将基于尖峰宽度和平均射击频率基于尖峰宽度和平均射击频率的假定主要细胞和推定的中间神经元分类为推定的中间神经元。< 0.4 ms or average firing frequency >5 Hz,占记录细胞的11%)。与啮齿动物和蝙蝠海马的相似记录一致,推定的主要细胞通常对应于特征空间中的细长簇和双峰间尖峰间间隔分布,而推定的中间神经元对应于更多的对称簇和更多对称的簇和尖峰间间隔分布。从五只蝙蝠的背侧海马中记录了总共373个良好的单元(177个涉及社会群体1的实验,以及77个来自涉及社会群体2和119的实验中的77个。
用于无线钙成像的显微镜与先前针对埃及水果BATS25所述的显微镜相似。简而言之,显微镜由3D打印的材料(黑色树脂; FormLabs)与市售的光学和电气组件52组合制成,并在我们的实验室组装。设计文件,零件号和软件可在GitHub(https://github.com/gardner-lab/finchscope和https://github.com/gardner-com/gardner-lab/video-capture)上公开获得。Excitation light is emitted by a blue LED (470 nm peak; LUXEON Rebel) and collimated by a drum lens (45-549, Edmund Optics), before passing through the excitation filter (3.5 mm × 4 mm × 1 mm, ET470/40x; Chroma) and a dichroic mirror (4 mm × 6 mm × 1 mm, T495lpxr, Chroma).梯度折射率(GRIN)物镜(GT-IFRL-200-INF-50-NC,Grintech)将激发光集中在样品上(0.5 Na)上。通过物镜收集的荧光是通过二角镜传输的,一种发射过滤器(4 mm×4 mm×1 mm,ET525/50m,色度),并通过出色的双重透镜(45-206,Edmund Optics)聚焦到模拟CMOS传感器(MB001; 3rd Eye cctv)上640×480像素。可以通过无线发射机 - 接收器夫妇(TX24019,100 mW)进行帧,整个系统(LED,CMOS和发射机)由轻巧的消费量3.7 V,300 mAh Lithium Polymer电池提供动力,在平均成像LED强度下稳定录制的稳定录制,以较少的成像启动(较少的成像)(比100 µ µW)(比100 µ µW)。该系统通过使用不同的载波频率与多个显微镜的同时流媒体兼容。NTSC视频和同步信号(由Master9生成,请参见上文)都通过USB框架抓取器数字化,并使用自定义Software52获取。USB框架获取器被封闭在可以通过电缆连接到接收器或直接连接到接收器的定制数据采集框(DAQ)中。
手术程序的进行类似于先前针对埃及水果BATS25所述的手术程序,并涉及注射和植入手术。CA-指示剂GCAMP6F的表达由Paav9.hsyn.gcamp6f.wpre.sv40(addgene)介导,并注射到背侧海马。简而言之,遵循上面“微培养植入物程序”部分中描述的麻醉,镇痛和头骨制剂相同的程序,以1.25μl的病毒为1.25μl的病毒以4 nl s -1的速度高于所需的坐标(5.8、2.8、2.8和2.6 mm,一个蝙蝠(CA1)或6.8,3.2和2.8,3.2和2.8 mmmmmmmmmmmmmmmmm mm,窦,中线和深度的侧面)。头骨中的注射开口充满了kwik-sil,并用缝合线封闭组织。然后,在注射后4周,按照先前针对埃及水果BATS25的程序进行了直径直径1.8毫米的笑手继电器透镜(130-004836,inscopix)的植入手术。使用附着在30 GA钝针上的真空泵吸入背侧海马上方的皮质。无菌乳酸铃声溶液以及可吸收海绵(Gelfoam,辉瑞)的压力施加到大脑上,以防止抽吸过程中出血。抽吸持续缓慢,直到视觉识别海马矿物的平行纤维。手术前,将继电器透镜通过轻型流动复合材料(Flow-It Alc,Pentron)的小桥粘在显微镜上。然后在从中成像的同时缓慢降低镜头+显微镜系统,直到观察到来自目标海马区域的荧光证据,为止, 通常从镜头的尖端到海马的背侧表面约100–200 µm。使用Kwik-Sil来密封晶状体和颅骨术边缘之间的空间,并在颅骨表面和骨螺钉上方施加混合的碳粉与牙科丙烯酸混合的碳粉,以将植入的透镜固定在适当的位置。小心地破碎了胶桥,以将继电器透镜与显微镜分开,并且在蝙蝠恢复的同时,继电器透镜的裸露表面被kwik-sil覆盖。接下来,在晶状体植入后2-3周,将微型显微镜与在麻醉下的继电器晶状体对齐,如先前所述25并固定在适当的位置。定制的3D打印防护外壳案例可确保防止损坏。
无线成像视频是通过连接到无线接收器的定制DAQ获得的,并与蝙蝠显微镜上的发射器进行通信。发射器,电池和跟踪标签(见上文)都包含在自定义的3D打印飞行案件中。对于每个成像的蝙蝠,两个DAQ同时获得了流帧,以最大程度地减少取决于发射器和接收器之间相对位置的流伪像。伪像通常会影响一个接收器的一小部分(平均值为1.43%),只要它们位于不同的位置,很少会影响两个接收器。我们通过从替代接收器中用完整的对应物代替了它们的完整对应物,从而恢复了大多数人工框架(见下文)。原始视频(640×480像素)以30 Hz的形式获得,然后在空间上倒下两个倍,并以10 Hz的速度下采样。使用ImageJ(V.1.53C)53中的自定义脚本进行预处理,并涉及伪影检测和恢复,背景补偿,运动校正,中值滤波和空间下降采样。简而言之,两个获取的视频之一被选为主(总是来自同一默认DAQ),另一个被选为备份。通过阈值标准检测到主要视频中的流文物,并用备份视频中相应的帧代替受影响的框架。接下来,通过减去其高斯过滤版本(σ= 80像素)并进行刚性运动校正来补偿大规模背景波动(MOCO54)。施加暂时的中值滤波(3帧),残留的伪影(平均0.13%)通常在静止期间发生,被视为掉落的帧,其荧光被插值。最后,视频在空间上被击倒了两个, 对应于每个像素约2 µm。与先前发布的方法相似的ROI分割和荧光痕迹的提取25,55,因此在下面的简要中进行了描述。使用针对单光子钙成像数据(CNMF-E)55的约束非负基质分解方法的适应ROI(推定的神经元),并在MATLAB中实现。所有提取的FOV使用以下参数(GSIG = 3,GSIZ = 13,MIN_CORR = 0.9,MIN_PNR = 50,RING_RADIUS = 10,backgky_to_to_to_neuron_factor = 1.5,没有空间或时间下降)。使用带有P = 1顺序的自回归模型(OASIS)对荧光轨迹进行反驳,并使用“约束的Foopsi”方法对其进行了反应。最后,对已确定的ROI进行了手动检查,以消除重复,不适当的合并和非细胞状ROI。所有随后的分析均对推断的尖峰率迹线进行,并在0到1之间归一化,并以1 s的移动平均值(归一化速率)平滑。通过将每个原始的时间迹线(C_RAW)乘以与每个ROI空间足迹成比例的缩放因子相乘,从而获得了图4C中所示的ΔF/F0痕迹。强度相关图像(图4B和扩展数据图14A)作为CNMF-E管道的一部分生成,并显示了局部像素相关性,反映了细胞体和无关背景的相关荧光发射。
在电生理实验结束时,给予蝙蝠的致命过量戊巴比妥钠,并用200 mL PBS(0.025 m,pH 7.4)灌注,然后用200 mL固定剂(PBS中的甲醛3.7%)。在灌注过程中,将微晶体留在原处。然后,几分钟后,仔细地缩回四极管,去除微训练,并解剖大脑并将其存储在固定溶液中1-2天。随后将固定的大脑移至PBS中的30%蔗糖溶液中,以进行冷冻保护。使用具有冰冻阶段的微型集体(HM450,Thermo Fisher Scientific)切割冠状切片(厚度为40μm)。对DAPI,富含Ca2添加的蛋白PCP4的染色(有关啮齿动物,请参见参考文献56,57,58,59,60,61)和小胶质细胞标记物IBA1(以啮齿动物的含量为单位,染色)和植入物周围的切片。简而言之,将切片在PBS+0.3%Triton X-100(PBS-X)中透化,然后在阻断溶液中孵育(PBS-X+10%驴血清)。在4°C与原始抗体(山羊抗IBA1、1:500,AB5076,ABCAM;和兔抗PCP4、1:200,HPA005792,Sigma-Aldrich)中孵育过夜后,将切片在PBS-X中洗涤,并在室温Antake-6中孵化,将其洗涤为120 andike Antake Antake Antake,1:1,000,Invitrogen,A32849;在最后10分钟的二次孵育中,添加了DAPI(1:10,000,Thermo Fisher Scientific)。将切片在PBS-X中洗涤,并用水性安装培养基(延长金抗固定式)盖上盖板。使用Axioscan幻灯片扫描仪(Zeiss)获取植入物周围每个部分的荧光图像,并用于将相对于海马子场(CA1和CA2)进行定位。根据PCP4荧光的组合确定了推定的Ca2 DAPI染色和与该物种BATS62的大脑图集的对应关系。通过在相邻的冠状切片中的四极管排列的序列重建确定四极位置。由于四轨轨道与冠状切割平面的平行不完全平行,因此每个部分都可以将每个电极的路径可视化(IBA1染色),因为每个部分在发炎组织的伸长片段。通过跟踪跨解剖冠状切片的组织神经胶质病来发现每个电极的尖端。在总共十二个四极管中(跨三个微晶)成功鉴定并定位在植入蝙蝠的背侧海马中。其余两个四座提供了推定的海马单位(以及可见的海马纹波),并包括在分析中,但不能与特定位置相关(包括254个单位中的7个)。采用类似的程序来确认对象实验中记录的蝙蝠在海马中的四极管的位置。在成像实验结束时,执行了类似的程序 - 排除PCP4和IBA1的染色,以确认瞄准镜头的靶向准确性和背侧海马区域CA1(一个BAT)或CA1 – CA2(CA1 – CA2(两个蝙蝠))周围的GCAMP6F表达曲线。
使用专用的超声麦克风(Earthworks M50,Earterworks)记录了实验室中的声音,该声音安装在房间上的一侧,该麦克风与前置放大器(Octamic II,RME Synthax)连接,并以192 kHz的采样率记录了音频数据。校正麦克风输出以达到最高96 kHz的平坦频率响应。使用MATLAB(MATHWORKS)的SoundMexTro(HORTECH)工具箱对录音进行控制,并使用自定义MATLAB脚本进行录制。检测回声定位呼叫类似于参考。48,进行如下进行。音频通滤(10-40 kHz)和Z尺寸的音频数据(96 kHz)被缩减采样。所有大于10 s.d.的事件被认为是潜在的回声定位点击,并使用MATLAB函数findpeaks确定,最小峰值距离为10 ms。其他宽带信号可能会污染点击的检测,但比通常在一个会话中发出的数千个回声定位调用要稀有得多。为了解决这个问题,我们利用了光谱域中的回声定位点击的相似性(对于这种BATS32物种),并在所有推定的点击量的第一个主要功率谱的主要组件定义的空间中寻找了最多的群集(K-均值,4个簇)。该群集和实际回声定位点击之间的对应关系通过在点击间隔分布中存在两个突出峰的存在证实,这与该物种的预期相一致(Intra Intra Intera Interval,〜20 ms; 〜20 ms; pair间隔; 〜100 ms,〜100 ms;扩展数据图12A)。检测到的回声定位信号在很大程度上与飞行蝙蝠的生产一致,因为(1)当蝙蝠接近麦克风时,其幅度的速度会增加(扩展数据图12d),(2)随着飞行动物数量的增加,回声定位堵塞的增加(图12E)和(3)和(3)和(3)和(3)和(3)和(3)和(3)和(3)和(3) 检测到的回声定位点击与飞行BAT9,63的机翼 - 束周期之间存在紧密的时间对齐(扩展数据图12F)。
所有分析均使用MATLAB(2021a,Mathworks)的自定义代码进行。
使用局部二次回归(1 s窗口)对所有RTL记录的蝙蝠的位置进行平滑。考虑到,当不飞行时,我们的蝙蝠通常不会通过爬行来改变其位置,从而进一步提高了跟踪质量,因此仍留在以前降落的地方。因此,我们根据加速度计信号(翼)中突出的8 Hz组件(翼)中的突出的8 Hz组件检测到飞行时期,并使用它们从第二平滑步骤中排除了所有飞行:在休息期间所有跟踪数据(即与翼型无关)的所有跟踪数据都通过移动中间窗口进一步平滑(5 s窗口)。对于每只蝙蝠,根据0.5 ms -1的速度阈值确定航班,并用于将蝙蝠的会话分为休息和飞行时期。蝙蝠倾向于在少数位置静置,通常(但不仅仅是)围绕房间的上角(图1B)。因此,我们使用团聚层次聚类在每次BAT的休息期间将位置簇生,至少为10 s,连接距离至少为10 s(扩展数据图2D)。通过计算每个2D空间箱中蝙蝠花费的样品数量(21×21箱,〜0.3×0.3 m)来计算占用图。没有平滑。在休息期间的勘探比(扩展数据图2C)计算为每个BAT访问的垃圾箱的分数(仅考虑轮廓箱,最小占用率为5 s)。靠近喂食器的时间的比例是计算为会话中花费的时间 <0.3 m from the feeder locations (Extended Data Fig. 2e). Correlations between spatial preferences (Extended Data Fig. 2f) were calculated as the Pearson correlation between rest occupancy maps (unrolled in 1D) across subsequent sessions or between different bats. Heading was defined for each flight sample as the direction of the instantaneous velocity vector in the xy plane.
A configuration of N bats in a given sample was defined as the vector of all positions (r1, r2, …, rN) and served as an input for state-space embedding by dimensionality reduction. Epochs in which all bats were resting were extracted and downsampled to one configuration every 3 s. This interval was chosen because it was approximately equivalent to the time between two flights (that is, a change in the group configuration). Euclidean distances between pairs of configurations were calculated and used as inputs for Sammon projection in two dimensions64, thereby obtaining a point in 2D (state space) for every input configuration of the group. Occupancy in the state space (Fig. 1c) was calculated on 80 × 80 spatial bins covering the range of obtained states and smoothed with a Gaussian kernel (σ = 1 bin). Considering the sparsity in the state space (that is, the highly clustered spatial preferences of the bats), states could also be approximated as discrete variables as follows. We pooled together all of the positions occupied by the bats during epochs of general rest and clustered them using agglomerative hierarchical clustering with a minimum of 10 s occupancy and 0.2 m linkage distance, therefore defining a set of discrete observed locations. In this way, each sample of general rest was associated with a configuration of discrete values (corresponding to the combination of bat identity × positional cluster identity). All of the possible states were calculated as (number of positional clusters)(number of bats). All visited states were defined as the effectively observed combinations, whereas all frequent states were defined as the configurations with occupancy higher than the s.d. of all of the state occupancies for that session (Fig. 1d, dashed line).
The spatial proximity between pairs of bats in a given session was quantified as the fraction of time in which the inter-bat distance was lower than 0.3 m. This value was corrected by considering that bats could be found in close proximity as a consequence of shared spatial (rather than social) preferences. Thus, we also calculated the average chance proximity for the same pair, by randomly circularly shifting in time the position of one of the bats in the couple. The chance distribution was generated by repeating this procedure 1,000 times. We calculated two measures of social proximity by comparing the empirical value of the spatial proximity and its chance distribution: a proximity index (corresponding to the difference between the empirical value and the mean of the chance distribution; Fig. 1g) and its associated P value (the fraction of shuffled spatial proximities that exceeded the empirical value; Fig. 1f).
For the analysis of spatial firing fields across all flights, we considered only active cells (n = 147 from three bats), with a minimum firing rate of 0.2 Hz during flight (minimum of 5 flights, at least 3 flights with spikes) and a minimum exploration ratio of 0.5 (as defined above, but across the whole room surface, see the ‘Preprocessing of tracking data’ section). We focused on the spatial firing in the xy plane (parallel to the ground), where most of the positional variance was concentrated. To compute 2D place-cell firing-rate maps, we projected all positions during flight onto the xy plane and calculated the occupancy-normalized firing rates as follows: we binned the 2D area of the room into fixed-sized spatial bins (0.15 × 0.15 m2) and calculated the occupancy (time spent in each bin) and the number of spikes fired in each bin. We smoothed both the spike-count map and occupancy map with a Gaussian kernel (σ = 1.5 bins) and calculated their ratio, bin by bin, therefore obtaining the firing rate per bin. Spatial bins in which the bat spent <200 ms were invalidated (white in Fig. 1j and Extended Data Fig. 4a), unless surrounded by at least one valid bin. Spatial information per spike65,66 was calculated by summing across all valid bins:
where pi is the probability of being in bin i, λi is the firing rate on the same bin and λ = Σipiλi is the average firing rate across all bins. A shuffling procedure was used to classify a cell as significantly spatially informative by comparing the empirical value of the spatial information to a spike-shuffled distribution. The shuffled distribution was generated by randomly shifting the timestamps of the cell’s spike-train circularly (after cutting rest epochs) and was repeated 1,000 times for each neuron. Significant place cells were defined as active neurons for which the empirical value of the spatial information exceeded the upper 95% confidence interval of its shuffled distribution.
As previously observed for solo bats or pairs of bats24,25, many flights of our animals followed along similar paths, typically traversed in only one direction. We took advantage of this feature and calculated spatial firing maps along tightly confined repeated trajectories (referred to as 1D flight paths). Flights were clustered into similar paths by using an analogous approach to that described previously25. In brief, flight trajectories were spatially downsampled to seven points per flight (first and last points corresponded to the take-off and landing positions, respectively). The Frechet distance67 between downsampled flights was used as a measure of flight similarity and similar flights were clustered by agglomerative hierarchical clustering. The linkage distance was set to 1.1 m after manual inspection of flight groupings. Spatial firing fields along flight paths (1D fields) were calculated for each repeated path and neuron with at least five flights and a minimum of four flights with spikes (n = 132 cells from three bats for collective foraging experiments and n = 116 cells from two bats during the object experiment). To compute the 1D fields, we used a similar procedure to the one adopted for 2D maps, applied in this case in only one dimension, to flight paths as 1D parametric trajectories rescaled between take-off and landing (bin size = 0.15 m). The firing rate was smoothed with a Gaussian window (7 samples) and spatial information was calculated across 1D bins as described above. A shuffling procedure was used to assess the significance of the spatial information of each 1D field. Similarly to what was described for 2D maps, spatial information was calculated on a shuffled spike distribution, generated by randomly shifting the timestamps of the cell’s spike train circularly (considering only flight epochs from the analysed path). Shuffling was repeated 1,000 times for each neuron and path (1D field). Significant 1D fields were defined as those for which the empirical value of the spatial information exceeded the upper 95% confidence interval of its shuffled distribution after applying Bonferroni correction for the number of paths examined for that neuron. The stability of 1D fields within a session (Fig. 1l) was measured by splitting each path into two random halves of repeated flights, separately calculating 1D fields on each half (Extended Data Fig. 4b) and calculating the Spearman correlation between corresponding halves.
Social modulation of firing during flight of the recorded bat was tested using three complementary approaches: (1) a stepwise GLM; (2) a test for firing differences between social and non-social flights anchored to specific take-off and landing locations—explicitly controlling for positional changes; and (3) a conservative test using modulation scores that aimed to identify social modulation in cases of minimal changes of kinematic variables (position, head direction and acceleration). We focused on the time periods around take-off and landing because these were associated with the largest fraction of spatial selectivity, and, furthermore, take-off and landing locations naturally constituted points in space were behavioural and positional variability was minimal (Fig. 1b), therefore enabling rigorous assessment of social modulation. Flights were divided into social and non-social using an empirically derived distance threshold (Fig. 2a), unless otherwise stated: all flights landing closer to a bat than 0.6 m were classified as social, whereas all flights landing further than 0.9 m were classified as non-social. The three approaches are explained below and are consistent with a significant modulation of hippocampal activity by the social nature of the bat’s spatial behaviour.
Approach 1 using GLM. The aim of this analysis was to test whether the social nature of a flight had significant explanatory power in predicting the firing rate of hippocampal neurons across all of the flights executed by the recorded bat in a given session, under the null hypothesis that simpler models, including the position of the recorded bat as explanatory variable, could fully explain the variance in firing rate. Social modulation of firing was tested across all flights using a stepwise GLM68. The stepwise procedure aimed to build a simple model that tries to explain firing rate around take-off or landing—for all of the flights—with the fewest possible explanatory variables. We allowed for the fact that firing modulation induced by the social nature of a flight could happen, for each cell, at different timepoints around take-off and landing, and first determined the optimal time bin for each neuron. We therefore first divided flights into social and non-social on the basis of the nearest-neighbour bat distance at landing (see above). We next systematically tested for differences in the mean firing rate between social and non-social flights using a sliding window of 500 ms around take-off and landing ([−1 s, +1 s], 100 ms increments) using the conditional C-test for Poisson means69. For each cell, we then considered the time bin with the lowest P value for further analysis. We built a model using the number of spikes in the optimal time bin as a response variable and three explanatory variables: x and y position of the recorded bat at the centre of the optimal time bin (positional coding) and the social nature of the flight (social versus non-social, using the distance for non-social flights to >0.6 m,在这种情况下包括所有航班)。我们仅考虑活性细胞(来自三个蝙蝠的n = 162),在整个会议过程中最低平均点火率为0.2 Hz,仅包括至少40次飞行(总数)和每类20次飞行(社交,非社交)的会议。我们将MATLAB函数逐步GLM考虑,将泊松分布视为响应变量的分布,将日志函数作为链接函数。逐步过程始于恒定的截距模型,并迭代地添加或删除术语(x,y和社会类别),其在解释响应变量时的统计意义。使用偏差测试68,70在逐渐更大的模型上进行比较,该模型测试包含更多解释变量的模型是否比更简单的模型要好得多。这使我们能够计算出比仅包括位置和/或恒定术语(恒定术语)更简单模型的单元格的百分比。
方法2基于发射差异而没有位置差异。该分析的目的是测试飞行的社会性质是否会导致特定起飞和着陆位置周围的点火率发生重大变化(与以前考虑所有起飞和着陆点的分析相比),同时控制模式时记录的蝙蝠位置的变化。我们利用了一个事实,即起飞和着陆位置自然聚集在空间中,并系统地评估了这些锚固点周围神经元的活动,从而迭代地将相同的步骤应用于神经元和锚定位置定义的对。首先,我们将空间聚类应用于记录的蝙蝠的所有静止位置(请参见上文),并仅保留从聚类位置的飞行(与大多数飞行相对应;扩展数据图2D)。结果,我们在起飞和降落时获得了一系列位置簇,每次都对应于与一组限制的位置相差或收敛的反复飞行。然后,对于每个位置群集,我们应用了以下过程。如上所述,我们对社交和非社会飞行进行了分类,并仅保留了每类至少五次飞行的位置群集。接下来,我们使用条件C检验并应用Bonferroni校正了测试窗口的数量,在起飞或着陆周围的滑动窗口的平均发射率差异([-1 s,+1 s],100毫秒的增量)对社交和非社会飞行之间的平均发射率差异。对于每个单元格和起飞位置的情况,我们将最低p值的时间箱视为最佳时间箱,以进行进一步分析。在着陆时, 取而代之的是,我们优先考虑在降落之前完全限制的时间窗口,并且仅在没有发现明显的射击差异之后考虑到降落后。我们仅包括在所有飞行中的最佳时间窗口中平均发射速率最小的电池(n = 135,来自三个蝙蝠)。一旦发现了最佳时间箱,就对应于社交上的点火率与非社会飞行之间的显着差异,我们测试了记录的蝙蝠位于最佳时间箱中心的位置的显着差异。这是通过使用简单的置换测试在社交与非社会飞行过程中分别测试X,Y和Z的差异来完成的。如果三个坐标中的任何一个显示小于0.05的P值,我们认为位置有显着差异。主文本中报道了细胞百分比。
基于调制分数的方法3。该分析的目的是在一种更为保守的方法之后,在社交和非社会飞行过程中表现出始终如一地调节点火率的神经元,同时表现出最小的位置变化,指向和加速度的变化。为此,我们实施了一个程序(调制得分计算;扩展数据图6),这使我们能够(1)在相同的统计框架内,使我们能够最小化社交数量与非社会飞行的数量与非社会飞行数量与非社会飞行的数量之间的任何潜在不平衡以及(2)测试差异(射击,位置,位置,头部和加速)之间的差异。调制得分的计算是按照所有活性神经元的相同步骤进行迭代执行的,并且在起飞和降落时满足包含标准的所有锚点(见下文)。如上所述,我们将航班分为社会和非社会活动,每个类别至少需要五次飞行以进行进一步分析(中位数为12,而每个类别的9次飞行)。首先,我们使用上述相同的步骤(再次对经过测试的窗口的数量应用Bonferroni校正),确定了根据航班的社会性质找到对射击的重要调制的最佳时间箱。我们仅包括在所有飞行中的最佳时间窗口中平均发射速率最小的电池(n = 135,来自三个蝙蝠)。找到最佳时间箱后,我们计算了时间箱(500毫秒)内的尖峰数,以及在时间箱中心的记录蝙蝠的位置和标题角度和每个飞行时间箱内的平均绝对加速度(由板上加速度计提供)。接下来,我们选择了所有可用航班的子样本,该飞行由五个随机选择的社交航班和五架随机选择的非社会飞行制成,并计算出来(1) 平均点火率之间的差异;(2)平均位置之间的距离;(3)平均标题角之间的差异;(4)平均加速度之间的差异,在相同的五个社交与五个非社会飞行中计算平均值。这四个差异中的每一个都被认为是该特定子样本的经验价值,并与通过随机定位飞行的社会性质获得的100个改组集进行了比较。如果社会和非社会飞行之间的相应差异大于相应的洗牌值的95%,则该特定子样本的关注变量(射击,位置,标题或加速度)被认为是显着差异的。我们重复了该过程100次,每次抽样五个社交与五个非社会飞行的不同子集,并且每次都计算射击,位置,标题和加速度差异的重要性。每个检查的单元格和锚定位置的调节得分计算为四个数字(触发,位置,标题,加速度),量化了子采样的派别,在该子次采样中,相应变量显示出显着差异(例如,触发调制得分为0.7表示,在100个亚采样中,在70分中,我们在平均射击中有显着差异,我们发现了围绕社交和非socecip的平均触发范围的差异。我们认为,如果飞行的社会性质(与位置,标题和加速度的最小变化)所调制的单元格 - 如果放电调制得分大于0.5(所有调制单元的平均0.7;扩展数据图7),所有剩余的分数(位置,标题和加速度)的所有剩余分数(平均0.5)均小于0.2(平均0.2)(所有调制单元覆盖了0.2)。在起飞之前或着陆后,未考虑将标题的调制得分置于集中的时间箱 (少数),因为这些垃圾箱未定义标题。在给定锚定点(图2D,g,k,k,k,k,k,k,k和图中的签名值的绝对值)上发射速率的调节值(与得分相反)的平均差异是在所有分布中的平均频率(典型的平均分布)校正的频率(典型的平均频率),计算出平均社交和非社会飞行之间的差异,否则将百分比。尽管这种使用调制分数的方法可低估受社会因素调节的细胞的比例(因为它有效地排除了其他因素也对细胞进行调节的细胞,例如加速和标题,这些细胞也可以在社会上受到调制),但它提供了与社会调制的综合评估和位置调节的综合评估。
根据上述部分所述的类似程序,对涉及三个蝙蝠和移动对象的实验进行分析,并使用完全相同的方法(调制得分,方法3)进行。为了避免受到社会反应的污染,对物体的调节进行了评估,考虑到没有蝙蝠在没有蝙蝠的情况下独家飞行降落在物体附近。如上所述,对于每个牢房和起飞或着陆位置,我们采用了一个迭代程序,以找到最佳的时间箱进行进一步分析,并采用了每次飞行数量最少的航班和尖峰的类似标准。通常,同一位置周围的单单元响应概况往往在物体存在与降落处的蝙蝠时大大不同(84%BAT调制和71%的对象调制显示明显不同的响应,P< 0.05 empirical data versus shuffled flight identities; some example responses are shown in Extended Data Fig. 8d).
The aim of this analysis was to investigate whether the modulation of firing during social versus non-social flights could be explained by the presence or absence of a specific bat at the landing spot, regardless of other bats. To test this hypothesis, we simply repeated the above analysis by replacing the nearest-neighbour bat distance at landing with the distance to a specific bat (termed as the target bat), iteratively testing all of the bats that participated in the session (minimum of 5 flights to target bat: landing distance <0.6 m; minimum of five flights not to target bat: landing distance >0.9 m)。我们采用了这种方法,遵循蝙蝠组行为的结构,在这些结构中,通常将不同蝙蝠在特定位置的位置相关。然而,这种方法使我们能够确定每个特定目标蝙蝠发生足够实例以评估潜在身份选择性的情况(图2L,m中的“分数相同”的点相同)。因此,下面的分析主要旨在理解在特定蝙蝠是调制的主要驱动力的假设下获得的效果是否可与或大于假设任何蝙蝠都在驱动调制的效果的效果相当。我们遵循了上面对每个目标BAT进行的分析,并使用足够的飞行(见上文,来自三个蝙蝠的n = 142个单元)。首先,我们寻找的细胞在放电方面存在显着差异并且位置没有显着差异(方法2)。其次,我们遵循了更保守的排除方法(调制得分,方法3;见上文)。由于该过程的迭代性质,可以通过不同的目标蝙蝠和不同的锚定位置调节单元格({cell,location,bat})。但是,我们发现大多数细胞都是围绕单个位置(79%)和单个目标蝙蝠(75%;扩展数据图9i)调节的,从而强调了海马神经元活动的选择性。在图2L,M中显示的其他分析中,我们评估了与社交与非社会飞行之间的一般区别相比,特定目标BAT的点火率调制变化的重要性(图2L)和与其他蝙蝠进行了比较(图2M)。为了评估与其他蝙蝠的发射率调制变化的重要性,我们为每个神经元计算了给定目标BAT的显着社会调制。发射调制得分在同一时间与其他目标BAT相对应 (我们将分析限制在至少八次飞往目标飞行的细胞中,八个飞行未靶向;图2M),并测试了两者是否有显着差异(Wilcoxon签名的秩检验)。我们还计算了基于原始目标蝙蝠进行分类时以及基于不同的目标蝙蝠时,我们还计算了具有相同类别的航班百分比(目标,而不是目标),因为两个蝙蝠有可能始终在同一位置同时存在(图2L,m,颜色代码)。在类似的分析中(图2L),我们检查了特定BAT获得的调制值与在同一时间箱中获得的社交和非社会飞行的调制值不同。为了测试这两种条件之间的显着差异,我们排除了对触发调制值更改符号(从增加到抑制作用,反之亦然)对的6%(5分)(58),当考虑社交,非社会而不是目标,而不是目标,而不是目标),并再次测试了两个值之间的显着差异(Wilcoxon签名的绝对值)。为了分析记录的蝙蝠与不同的目标蝙蝠之间的社会接近性(图2N),我们计算了记录的蝙蝠和目标蝙蝠之间的接近性指数(纯粹的行为度量)(纯行为量度)(请参见上文)(与海马活动的显着调节)以及记录的蝙蝠和“不同的蝙蝠”之间的差异相同(因此与每次频繁的速率相关)(因此,在per cyr bat and after vers after by and after vers and after by a verty bece and a verty a verty a verty的差异很大,都不是相关的。为了避免歧义,我们仅包括一个单个目标蝙蝠调节的单元(n = 30个蝙蝠),并认为是独特的不同蝙蝠,满足了最小飞行数量的纳入标准,并且与最多的飞行数量相关(这意味着可以测试不同的蝙蝠,但不会引起重大的射击调节模拟)。接近指数之间的差异通过成对比较(Wilcoxon签名秩检验)测试。为了显示效果的大小,将图2N中的接近指数归一化为植入的蝙蝠和所有其他蝙蝠之间的中位数接近指数,而与神经调节无关。对于所有社会调制的单元,我们控制了会话中的飞行时间与飞行不实现目标的时间之间的差异(在58个单元中只有8个单元在飞行时间之间显示出显着差异,P< 0.05, Wilcoxon rank-sum test), suggesting that, overall, the modulation was not due to unstable recording of neural activity throughout the session, consistent with the fact that firing patterns were generally very stable (Fig. 1l).
Simulations were performed by combining the observed behaviour of implanted bats during collective foraging with modelled cell responses. All of the sessions that were included in the analysis of single-unit responses were also used for simulations. We performed two sets of simulations: one for evaluating the responses of different cell classes and one for evaluating the decoding performance from the activity of simulated cells. The two sets differed only in the number of simulated cells of each type and in the distribution in space and time of spatial and social responses (described below). The firing rate of each neuron was modelled on 200 ms time bins as an inhomogeneous Poisson process with rate λ(t) given by the contribution of spatial and social responses. In particular, for each time bin centred at ti:
The above equations describe spatial fields with maximal firing λc at the centre xc of the 2D field and width σc. w is a windowing function that ensures firing at rest decays within 0.5 s from take-off or landing. ‘Social’ responses were simulated as Gaussian-shaped changes in firing rate (value λs) happening around take-off or landing (ts) and lasting for σs seconds, conditioned to the presence or absence of a bat at the landing spot (b term), using a distance threshold of 0.6 m. Different cells classes could be generated by modifying the parameters of the model. Canonical place cells were generated by setting λs = 0; pure social cells were those with λc = 0; conjunctive cells were defined by setting λs = ±λc and b(ti) true only if (x(ti) − xc)2 ≤ σc2, that is, firing was modulated both positively or negatively by the presence or absence of a bat, but only within a given spatial field (the sign of the social modulation was positive with 0.5 probability). To evaluate the general properties of modelled cells (Extended Data Fig. 10e), we simulated 50 cells per session and per implanted bat. These cells were randomly selected from the three categories defined above with probabilities 0.2 (spatial), 0.2 (social) and 0.6 (conjunctive), given the sparser responses of conjunctive cells. Parameters of the model such as the baseline firing rate, field width, firing rate at the centre of the spatial field or rate change for social versus non-social flights were derived from the experimentally observed values (λspont = 0.4 Hz, λc = 8 Hz for spatial cells, λs = 4Hz for social cells, λs = ±λc = ±4 Hz for conjunctive cells, σc = 50 cm, σs = 0.5 s). ts was randomly selected to be at take-off or landing, whereas xc was uniformly distributed across the 2D extension of the room. Activity from the simulated cells was analysed with exactly the same methods adopted for real cells and used to quantify spatial tuning and social modulation. For the second set of simulations (Extended Data Fig. 10f), 100 cells were simulated for each session and implanted bat, chosen at random from the three categories (~33 cells per class per session and implanted bat). Given that we were interested in decoding the landing position and the social nature of flights at landing, xc was randomly sampled from the relevant landing locations of the bats (min 5 flights) and ts was fixed at landing only, such that spatial, social and conjunctive responses were all concentrated around landing. Decoding of the landing location and or of the social nature of flights was performed by training multiclass support vector machines, by using the average activity of simulated cells on a [−0.5, 0.5] s time window around landing. Decoding accuracy was evaluated by fourfold cross-validation for increasing the numbers of cells from each of the modelled classes.
We carefully examined several alternative explanations for the social modulation involving the interplay between identity and reward (Extended Data Fig. 11). First, we looked for evidence of leading-following dynamics (Extended Data Fig. 11a), whereby flights of a given bat to reward locations reliably preceded or followed flights of another bat to the same location. We tested each pair (bati, batj) twice, corresponding to one bat leading and the other following or vice versa. We quantified the interval between bati landing on a reward location and batj taking off towards the same location, and we compared the median of observed intervals with that of a shuffled distribution in which the take-offs of batj were circularly permuted, therefore preserving the inter-flight time. We repeated this process 100 times and calculated the fraction of shuffled sets yielding a median interval smaller than the empirical value. To consider a relationship as significant, we required the aforementioned fraction to be <0.05 and a minimum of 5 intervals between landing and take-off shorter than 12 s for each session. Next, we tested different explanations for the modulation of neural activity potentially associated with reward and described in Extended Data Fig. 11b–e. Potential reward blocking was tested by looking at the landing locations at which cells were modulated (Extended Data Fig. 11b); potential disturbing (scrounging) was examined by looking at the take-off locations preceding landing at which cells were modulated (Extended Data Fig. 11c). In both cases, we found little overlap between the locations that would be expected if only the reward caused the response. Next, potential ‘next reward availability’ was tested by looking at the probability and timing of next flights to reward when the target bat was either present or absent at the location where cells were modulated (Extended Data Fig. 11d); potential disturbance of the target bat was investigated by looking at the distribution of the time intervals from last reward of the target bat relative to the time of neural modulation (Extended Data Fig. 11e). Finally, the percentage of cells directly responsive to the reward was calculated for a subset of the single units, recorded with a probabilistic reward delivery and with at least 5 rewarded and 5 unrewarded flights (mean 42 versus 29, respectively; 73 neurons from two bats). The average firing profile was calculated in a [0–3] s time window after landing for trials with or without reward delivery (happening ~1 s after landing), when the bat landed on the same reward location in the absence of any other bat. The absolute difference, across the window, in the average number of spikes between rewarded and unrewarded flights was compared with 100 shuffled values of the same difference obtained by a similar procedure, where the identities of rewarded and unrewarded flights were randomly permuted. A cell was considered to be significantly reward responsive if less than 5% of the shuffled values were larger than the empirical value.
Modulation of neural activity under stationary conditions was evaluated around take-off of other bats. To avoid ambiguous events, we considered an interval from −1 to +1 s around each take-off and excluded all take-offs associated (1) with intersected intervals or (2) with intervals in which the recorded bat was also flying, which were very rare. All of the remaining intervals were therefore associated to the take-off of one single bat and disjointed with other intervals (the distribution of the number of valid events per session is shown in Fig. 3a). To account for the fact that hippocampal activity could be influenced by the overall movement of the recorded animal, in our main analysis, we considered only events characterized by low mobility of the recorded bat in the [−1s, +1s] interval around take-off (all flights and periods of high mobility are shown in Extended Data Fig. 13). To assess the recorded bat’s mobility, we used an on-board accelerometer. We calculated the vectorial norm of the three-axis acceleration recorded from the accelerometer and subtracted it to g (9.81 m s−2). All flights in which the absolute deviation from g exceeded 0.03 m s−2 in any of the samples of the considered interval were excluded (Fig. 3b). only cells with a minimum of 20 low mobility events (mean across cells: 155) and a minimum average rate of 0.2 Hz across the session were considered for further analysis (n = 177 from three bats). This enabled us to effectively behaviourally clamp the recorded bat and exclude modulation of neural activity by self-movement. Significant modulation was assessed by systematically comparing firing rates in a sliding window around others’ flights (500 ms duration, 100 ms steps, range: −1 s, +1 s around take-off), with the average firing rate across the whole interval. A cell was defined to be significantly modulated if the firing rate was significantly different from the average firing in any of the tested time windows (P < 0.05, Wilcoxon signed-rank test after Bonferroni correction for the number of tested windows). Comparison of hippocampal responses around others’ flights with or without echolocation (Extended Data Fig. 13e) was carried out for the subset of significantly modulated cells (as defined above) that contained enough trials of both types (minimum of 20). The delay between responses was calculated as the time lag giving the maximal cross-correlation between response profiles, considering only cells with maximal cross-correlation larger than 0.2 per sample. The click-triggered PSTH (Extended Data Fig. 13f) was calculated for the significantly modulated cells by considering the firing rate around echolocation clicks (minimum of 150 clicks, separated by at least 80 ms to avoid double counting within a click pair) emitted when no bats were flying and normalized to the baseline firing rate. For generating the shuffled trace, the time instants corresponding to the number of detected clicks were randomly sampled from the same epochs of no flight. The magnitude of the modulation for close versus far take-offs (Extended Data Fig. 13d) was measured for each cell as follows: first we selected the subset of cells with enough repetitions (minimum 10) of both low mobility close flights (<1 m take-off distance) and low mobility far flights (>1 m起飞距离)。然后,我们计算了这两个类别的起飞事件([-1s,+1s])周围的平均点火率曲线。然后,将调节的“大小”计算为每个单元的“平均点火率曲线(接近与远)之间的标量产物”和模板响应(定义为所有调制单元的平均点火速率)之间的平均发射速率。相似的定义,通过标量产品的定义,用于计算出选择性指数的响应量(请参见下文)和CAN 2(CASE)的最终响应(参见CACARTION)和CACINTIST(参见CACAREUTION)的响应幅度(ca)和CASINT(CACE)(ca)(CACE)之间的cation(CASE)。在三种不同的条件下计算了他人起飞过程中社会调制的选择性指数:(1)记录的蝙蝠位置的选择性(固定);(2)选择起飞的蝙蝠身份的选择性;(3)鉴于记录的蝙蝠的位置,对蝙蝠的身份的选择性(图3F;见下文)。记录的蝙蝠的位置被认为是一个分类变量,与其他蝙蝠起飞时记录的蝙蝠占据的位置群集相对应(有关位置聚类,请参见上文)。在所有情况下,我们仅考虑与同一类(位置或BAT身份)至少重复十次重复的事件。丢弃了少于十次重复的事件,并且仅考虑其余类别计算选择性指数。结果,只能针对那些至少两个位置和/或身份在排除后仍保留两个位置和/或身份的细胞(分别n = 124、110、113)。计算进行如下:在给定条件(位置或身份)下单元的平均响应计算为在[-1 s,+1 s]间隔的平均触发速率和模板响应之间的平均点火率之间的标量产物(有关响应的幅度,请参见上文)。为了计算选择性指数, 将跨不同位置或身份的一组响应标准化以假定正值,并如前所述计算了选择性指数71,72:
其中n表示不同条件(位置或身份)的数量,而RI表示该条件下单元的平均响应。通过在位置或身份随机置换后重复上述步骤来计算100个洗牌选择性指数的分布。当选择性指数的经验值超过其洗牌分布的上部95%置信区间时,将一个单元定义为给定位置或BAT身份的显着选择性。通过系统地将每个位置视为单独的子集并计算从该子集的BAT身份的选择性索引,从该子集中进行了类似的选择,对给定位置的选择性指数的计算也类似地执行。
与成像会话有关的所有行为分析遵循上述相同的方法,因为在电生理学和成像的情况下,实验的结构在很大程度上是相同的(从碗或四个喂食器觅食的6或7个蝙蝠),主要区别是成像会话的较短持续时间(约60分钟)。为了分析成像过程中的社会和空间响应,我们关注的是至少有一个登陆位置的会议子集,其中至少有一个成像蝙蝠的刻板印象和一致的行为,用于社交活动(N = 24个FOV,跨20个FOV,跨20个会话,同时进行了一个或两个不同的蝙蝠,总计3种不同的bats)。特别是,我们需要每种类型的至少五次飞行(社交与非社会性),并且在着陆位置,前进方向(在降落前的[-1,0] s窗口上平均)和蝙蝠的整体移动中没有显着差异(在[0,2]使用[0,2]窗口测试的G <0.使用p <0.使用GAT的整体移动中(量化为加速度计信号的绝对偏差)。一旦找到了可分析的着陆位置,我们通过比较了在[-1,2]的时间窗口上的归一化发射率(上述定义)来测试了每个提取的ROI进行社交调制(定义的)平均,该时间窗口围绕着陆的时间窗口进行降落,以进行社交与非社会飞行相对于非社会飞行(如果使用p <0.05,则被认为是社交调节的)。对于主成分分析和解码,我们认为在社交和非社会降落的标准化射击率和非社会降落的标准化功能上,在同一[-1,2]的时间窗口上平均。因此,每个着陆均与N×F矩阵有关,其中n是社会调制的细胞(或匹配的社会未经调节神经元数)和f飞行数量的数量,每个飞行数量与阶级相关联(社交与非社会)相关联。前两个主要组件都用于可视化(图4E,左) 并用于计算社交活动与非社会飞行的活动质心之间的距离(图4E,右)。通过旋转给定的会话旋转所有点(社交和非社交),从不同会话中汇总了来自不同会话的数据并在同一主体组件平面中表示,以使社交飞行的活动质心在负PC1轴上。该方法用于社会调制以及未调制的细胞作为对照。为了解码社交与非社会着陆点,活动矩阵用于训练逻辑回归分类器。使用四倍的交叉验证计算精度。在对社会反应分析的同一组FOV中定义了空间调节的细胞,因为使用相同的[−1,2] S时窗口相对于地覆盖了相对的相同,在房间中,ROI与房间中最常见的两个位置相对于一个最常见的位置中的一个与另一个最常见的位置相比,在一个最常见的两个位置中显示出显着不同的活性(平均= 31%的空间调制细胞)。如上所述,通过训练活动矩阵上的逻辑回归分类器进行了空间解码,在这种情况下,在这种情况下,在房间中两个最常见的位置降落时,活动是在这种情况下计算的。解码准确性(空间或社会)是针对不同细胞集(社会调制,空间调制,未经调制或社会而非空间调制的)计算的。请注意,对于社交和空间解码,机会级别为0.5。
没有形式的方法应用于预性样本量,采用的样本量与类似研究使用的样本量相似。在分析过程中未实施实验会话的随机性,并且对实验条件没有视而不见。除非另有说明,否则使用非参数测试(Wilcoxon Rank-sum测试,Wilcoxon签名级测试,引导或随机测试)进行所有统计比较。除非另有说明,否则测试是两尾。在适当的情况下,使用Bonferroni或Tukey校正对多次比较进行了调整。
有关研究设计的更多信息可在与本文有关的自然投资组合报告摘要中获得。