TY - JOUR
T1 - Intracortical generators of the flash VEP in monkeys
AU - Kraut, Michael A.
AU - Arezzo, Joseph C.
AU - Vaughan, Herbert G.
N1 - Funding Information:
Visual evoked potentials (VEPs) are often used to assess the integrity of the human visual system. Despite the widespread clinical application of these measures, the neural mechanisms that generate the surface recorded wave form have yet to be determined. Although intracranial recordings of VEP in humans have been made (Vaughan 1966), it is not feasible to carry out the detailed intracortical laminar analysis that is required to define the VEP generators. An alternative approach is analysis of the VEP in the non-human primate. The morphology of the flash VEP in the monkey is stable over time (Vaughan and Gross 1969; Snyder et al. 1979) and is similar in many respects to that recorded in humans (Vaughan 1966; Vaughan and Gross 1969; Creel et al. 1973). The goal of the present study is to analyze the intracortical depth profile of the flash VEP in the monkey, exploiting 1 Supported in part by Grants HD01799, MH06723, and NRSA Training Grant MH15788 from the U.S. Public Health Service.
PY - 1985/7
Y1 - 1985/7
N2 - Flash visual evoked potentials (VEPs) in unanesthetized monkeys were recorded from the cortical surface and from closely spaced intracortical sites together with associated multiple unit activity (MUA). The VEP depth profiles were subjected to current source density (CSD) analysis to delineate the laminar pattern of transmembrane current flows manifested by extracellular sources and sinks. The initial surface recorded components (P15 and P18) were generated subcortically within the thalamocortical radiations. The distribution of current sources and sinks associated with two subsequent surface negative components, N24 and N40, demonstrates their generation within laminae IVA and IVCb respectively, both parvocellular thalamorecipient layers. Oscillatory potentials resembling those seen in human VEPs are observed riding on N40; analysis of MUA in conjunction with sources and sinks coincident with these wavelets provides evidence that they derive from both thalamocortical and cortical activity. MUA in the 20-60 msec range shows phasic increases throughout lamina IV, which are maximum in amplitude within lamina IVA. This increased firing is concurrent with the sinks observed within the parvocellular thalamorecipient sublaminae IVCb and IVA. A subsequent component, P65, coincident with a decrease in MUA to below the spontaneous level co-located with a lamina IVCb current source, probably arises from intracortically generated inhibitory activity within IVCb. The next VEP component, a surface negative potential at 95 msec, is coincident with current sources and sinks in lamina III, and is consistent with stellate cell input to supragranular elements. VEP components after N95 are not associated with either MUA or CSD activity and are probably generated in extrastriate cortex. Human counterparts of the simian VEP are proposed.
AB - Flash visual evoked potentials (VEPs) in unanesthetized monkeys were recorded from the cortical surface and from closely spaced intracortical sites together with associated multiple unit activity (MUA). The VEP depth profiles were subjected to current source density (CSD) analysis to delineate the laminar pattern of transmembrane current flows manifested by extracellular sources and sinks. The initial surface recorded components (P15 and P18) were generated subcortically within the thalamocortical radiations. The distribution of current sources and sinks associated with two subsequent surface negative components, N24 and N40, demonstrates their generation within laminae IVA and IVCb respectively, both parvocellular thalamorecipient layers. Oscillatory potentials resembling those seen in human VEPs are observed riding on N40; analysis of MUA in conjunction with sources and sinks coincident with these wavelets provides evidence that they derive from both thalamocortical and cortical activity. MUA in the 20-60 msec range shows phasic increases throughout lamina IV, which are maximum in amplitude within lamina IVA. This increased firing is concurrent with the sinks observed within the parvocellular thalamorecipient sublaminae IVCb and IVA. A subsequent component, P65, coincident with a decrease in MUA to below the spontaneous level co-located with a lamina IVCb current source, probably arises from intracortically generated inhibitory activity within IVCb. The next VEP component, a surface negative potential at 95 msec, is coincident with current sources and sinks in lamina III, and is consistent with stellate cell input to supragranular elements. VEP components after N95 are not associated with either MUA or CSD activity and are probably generated in extrastriate cortex. Human counterparts of the simian VEP are proposed.
KW - flash VEP
KW - intracortical generators
KW - visual evoked potentials (VEPs)
UR - http://www.scopus.com/inward/record.url?scp=0021795722&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0021795722&partnerID=8YFLogxK
U2 - 10.1016/0168-5597(85)90007-3
DO - 10.1016/0168-5597(85)90007-3
M3 - Article
C2 - 2408876
AN - SCOPUS:0021795722
SN - 0168-5597
VL - 62
SP - 300
EP - 312
JO - Electroencephalography and Clinical Neurophysiology/ Evoked Potentials
JF - Electroencephalography and Clinical Neurophysiology/ Evoked Potentials
IS - 4
ER -