Lateral spread of neuronal activity within the motor cortex investigated with intracellular responses to distant epicortical stimulation.

Abstract

1) Lateral spread of activity within the motor cortex was examined by means of analyses of the direct cortical responses (DCRs) and intracellular responses to distant epicortical stimulation (EPICS) using cat encephale isole preparations. 2) DCRs to the EPICS at a distance of 1.5-6.5 mm consisted of initial small positive (Pd) and subsequent negative waves (Nd). The reversal of polarity in depths occurred at 400-550 µm for Pd' and at 150-250 um for Nd as well as for the initial negative wave elicited by near EPICS, 3) Intracellular responses to distant EPICS consisted of excitatory (EPSP) and inhibitory postsynaptic potentials (IPSP), disfacilitation (DF), and disinhibition (DI). Depth distributions of cells with EPSPs at two peaks in laminae II and V-VI, with IPSPs mainly in lamina III, and with DF or DI in laminae V-VI were the same with those by near EPICS. The inhibitory effects of distant EPICS on middle layer cells were much greater than those by near EPICS. 4) No linear relations of the latency of EPSPs or IPSPs to the depth were seen for distant EPICS. Instead, the latency increased in proportion to the lateral distance in EPSPs at a slower rate than in IPSPs compared in superficial and middle layer cells. 5) Several routes for lateral spread of activity were postulated. Most conspicuous are the excitatory route via horizontal axons in lamina I and the inhibitory route via laterally running axons in laminae II-III, which produce overall excitation of superficial layer cells and depression of middle and deep layer cells. Their possible role in phasic cortical arousal was discussed.

Vertical spread of neuronal activity within the cat motor cortex investigated with epicortical stimulation and intracellular recording.

“…There is therefore good reason to pursue this line of comparison. More detailed analysis will be dealt with in a separate paper (EzuRE and O5HIMA, 1985b), after registering in the next paper (EZURE and OsHIMA, 1985a) the neuronal responses recorded laterally to the stimulated site on the cortex and thus summarizing the patterns of response spread in both the vertical and horizontal directions.…”

“…As has been demonstrated earlier (cf. ADRIAN, 1936;CHANG, 1951) and will be described in detail in the following paper (EZURE and OsHIMA, 1985a), a positive component wave in DCR appears earlier than DCR-N when EPICS is applied distantly more than 2 mm from the recording site. It is conceivable that some DCR-P coexists with DCR-N to near EPICS, being masked by the latter.…”

“…By varying the distance of EPICS, a lateral or tangential spread of excitation and inhibition was examined. The lateral activity spread possibly conveyed via tangentially running axons in certain cortical layers will be elucidated in a subsequent paper (EZURE and OSHIMA, 1985a).…”

Differential Effects of Abnormal Tactile Experience on Shaping Representation Patterns in Developing and Adult Motor Cortex

“…Although trains of stimuli, such as those used in the present study, can produce different patterns of recruitment, most penetrations from which current trains are passed yield movement of a single body part; the movement of different body parts can occur with as little as ϳ100 m displacement of electrode position. These observations would suggest that activation of distantly located output neurons by direct current spread, transynaptically, or by engaging widespread afferent or intrinsic axons is minimal (Asanuma et al, 1976;Ezure and Oshima, 1985).…”

Mapping human brain networks with cortico-cortical evoked potentials

“…Specifically, studies in cat neocortex rarely observed antidromic activation following direct cortical stimulation [74]. Moreover, the majority of responses to direct cortical stimulation propagated from superficial lamina to deep lamina [74].…”