Intrinsic Connectivity in Area 18 of the Cat

  • Gunther Neumann
Part of the NATO Advanced Study Institutes Series book series (NSSA, volume 27)


In order to determine the organization of afferent and intrinsic connectivity in area 18 of the cat, latencies and scatter of single-unit responses to electrical stimulation of the primary afferents were analyzed. The units’ laminar positions were assessed by evaluating current source densities along the same recording track on the way back to the cortical surface.

Mono-, di-, and trisynaptic responses are discernible in the latency histogram after stimulation of the lateral geniculate nucleus. The monosynaptic responses can be subdivided into two classes according to their latency scatter. The low scatter of the disynaptic responses suggests that they arise almost exclusively from the low scatter monosynaptic activity.

The most prominent feature of layers I–III is the preponderance of disynaptic responses which are followed by trisynaptic activity in about 30% of the cells. The most striking properties of the infragranular layers are the high percentage of multispike responses and the large scatter of latencies between cells.

The wiring diagram that accounts for the temporal and spatial properties of the analyzed responses shows strong and local connections from the input stage cells in layer IV to cells in the supragranular layers and in layer V. In addition, the supragranular and, probably also, the infragranular layers project onto themselves forming positive feedback loops.


Lateral Geniculate Nucleus Current Source Density Cell Somata Intrinsic Connectivity Supragranular Layer 
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Copyright information

© Plenum Press, New York 1979

Authors and Affiliations

  • Gunther Neumann
    • 1
  1. 1.Max-Planck-Institut für PsychiatrieMunichWest Germany

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