Properties of single neurons in the cat midsuprasylvian gyrus

Summary Responses of cells in the midsuprasylvian gyrus (MSSG) of cats were investigated following electrical stimulation of the central lateral nucleus (CL) of the thalamus and tooth pulp, low-threshold cutaneous or visual afferents. Electrical stimulation in CL induced excitation in many cells located in cortical areas 5 and 7. Cells in these areas also received input from somato-sensory and visual afferents. Cells in MSSG showed a wide convergence from tooth pulp, low-threshold cutaneous afferents and from the CL. The majority of wide convergent cells in area 5 were found in layers IV and V, while cells excited by CL and tooth pulp were found in layers II and III. Similarities were found between CL and tooth pulp evoked responses with regard to the excitation-inhibition pattern. The excitation evoked from CL and tooth pulp was less often followed by a hyperpolarizing potential compared to that seen after low-threshold lip, paw and visual afferent stimulation. Stimulation sites in the lateral parts of CL-evoked responses with the shortest latencies in area 5. In this part of the cortex, short latency synaptic potentials were found in cells in superficial layers. In the same area, synaptic potentials of short latency were also evoked by electrical stimulation of tooth pulp, lip and paw. Light-flash stimulation evoked responses with the shortest latencies in area 7. The results of this study demonstrate that putative nociceptive information reaches the parietal association cortex and that part of this input may be relayed via CL. We suggest that the excitatory influences of nociceptive and CL stimulation is related to behavioral arousal and attention mechanisms.Abbreviations AV anteroventral nucleus - CL central lateral nucleus - CM centre median nucleus - GL lateral geniculate nucleus - LD lateral dorsal nucleus - LP lateral posterior complex - MD mediodorsal nucleus - MSSG midsuprasylvian gyrus - OT optic tract - PAC paracentral nucleus - PF parafascicular nucleus - Po posterior thalamic nuclei - PP pes pedunculi - STT spinothalamic tract - VB ventrobasal complex - VA ventroanterior nucleus - VL ventrolateral complex - VMB basal ventromedial nucleus - VMH ventromedial hypothalamic nucleus - VPL ventroposterolateral nucleus - VPM ventroposteromedial nucleus - C.Max contralateral maxillary canine tooth - I.Max ipsilateral maxillary canine tooth - C.Mand contralateral mandibular canine tooth - I.Mand ipsilateral mandibular canine tooth - C.Lip contralateral upper lip - I.Lip ipsilateral upper lip - C.F.Paw contralateral forepaw - I.F.Paw ipsilateral forepaw - C.H.Paw contralateral hindpaw - I.H.Paw ipsilateral hindpaw - AP anteroposterior plane (in mm anterior to the interauricular plane) - ML mediolateral plane (in mm lateral to the midline)