Angelucci Alessandra, Levitt Jonathan B, Walton Emma J S, Hupe Jean-Michel, Bullier Jean, Lund Jennifer S
Department of Ophthalmology and Visual Science, Moran Eye Center, University of Utah, Salt Lake City, Utah 84132, USA.
J Neurosci. 2002 Oct 1;22(19):8633-46. doi: 10.1523/JNEUROSCI.22-19-08633.2002.
Contrast-dependent changes in spatial summation and contextual modulation of primary visual cortex (V1) neuron responses to stimulation of their receptive field reveal long-distance integration of visual signals within V1, well beyond the classical receptive field (cRF) of single neurons. To identify the cortical circuits mediating these long-distance computations, we have used a combination of anatomical and physiological recording methods to determine the spatial scale and retinotopic logic of intra-areal V1 horizontal connections and inter-areal feedback connections to V1. We have then compared the spatial scales of these connectional systems to the spatial dimensions of the cRF, spatial summation field (SF), and modulatory surround field of macaque V1 neurons. We find that monosynaptic horizontal connections within area V1 are of an appropriate spatial scale to mediate interactions within the SF of V1 neurons and to underlie contrast-dependent changes in SF size. Contrary to common beliefs, these connections cannot fully account for the dimensions of the surround field. The spatial scale of feedback circuits from extrastriate cortex to V1 is, instead, commensurate with the full spatial range of center-surround interactions. Thus these connections could represent an anatomical substrate for contextual modulation and global-to-local integration of visual signals. Feedback projections connect corresponding and equal-sized regions of the visual field in striate and extrastriate cortices and cover anisotropic parts of visual space, unlike V1 horizontal connections that are isotropic in the macaque. V1 isotropic connectivity demonstrates that anisotropic horizontal connections are not necessary to generate orientation selectivity. Anisotropic feedback connections may play a role in contour completion.
初级视觉皮层(V1)神经元对其感受野刺激的空间总和及上下文调制中对比度依赖性变化,揭示了V1内视觉信号的长距离整合,这远远超出了单个神经元的经典感受野(cRF)。为了确定介导这些长距离计算的皮层回路,我们结合了解剖学和生理学记录方法,以确定V1区域内水平连接以及V1的区域间反馈连接的空间尺度和视网膜拓扑逻辑。然后,我们将这些连接系统的空间尺度与猕猴V1神经元的cRF、空间总和场(SF)和调制周围场的空间维度进行了比较。我们发现,V1区域内的单突触水平连接具有合适的空间尺度,可介导V1神经元SF内的相互作用,并构成SF大小的对比度依赖性变化的基础。与普遍看法相反,这些连接不能完全解释周围场的维度。相反,从纹外皮层到V1的反馈回路的空间尺度与中心-周围相互作用的整个空间范围相当。因此,这些连接可能代表了视觉信号上下文调制和全局到局部整合的解剖学基础。反馈投射连接了纹状和纹外皮层中视野的相应且大小相等的区域,并覆盖了视觉空间的各向异性部分,这与猕猴中各向同性的V1水平连接不同。V1的各向同性连接表明,各向异性水平连接对于产生方向选择性并非必要。各向异性反馈连接可能在轮廓完成中起作用。