Learning and recall of form discriminations during reversible cooling deactivation of ventral-posterior suprasylvian cortex in the cat.

Abstract

Extrastriate visual cortex of the ventralposterior suprasylvian gyrus (vPS cortex) of freely behaving cats was reversibly deactivated with cooling to determine its role in performance on a battery of simple or masked two-

Synaptic transmission in the neocortex during reversible cooling

“…Indeed, a decrease of the number of single-unit spikes in responses to sensory stimulation during cooling has been consistently observed. 17,22,29,33,36,52 The other consistent and unambiguous effect of cooling was on the temporal properties of synaptic transmission. Even moderate cooling would lead to severe, if not total, destruction of the temporal structure of spike trains.…”

“…However, an extremely complicated picture of changes is expected in a cooled cortical area because of high temperature gradients measured around the cooled region in vivo 17,29 and because of differences between individual cells in the dependence of the basic membrane properties 54 and synaptic transmission on temperature. A complete block of spike generation is reached only when the temperature of the tissue is well below 10ЊC.…”

“…17,33 The neurons that are not cooled to that extent could be still in a hyperexcitable state rather than "inactivated". Because of the high temperature gradients, 17,29 moderately cooled, and therefore hyperexcitable, tissue will surround the region under the cooling device. For example, cooling the plate, positioned on the cortical surface, even to the freezing point (0ЊC) may result in only a local silencing of the region located within about 2 mm from the plate, while mixed effects -silencing of some cells but hyperexcitability of some others might occur in the surrounding regions.…”

The cryoloop: an adaptable reversible cooling deactivation method for behavioral or electrophysiological assessment of neural function

“…Objective measures of cooling induced deactivation are obtained using Brainwave Systems' 'Discovery' software to collect multiple channels of extracellular spike activity (e.g. Lomber et al, 1994Lomber et al, , 1996aMendola and Payne, 1993;Payne et al, 1991Payne et al, , 1996b, and calculation of a cooling block: normal ratio (B:N ratio, Malpeli, 1983). When B:N = 0, neurons are silenced during cooling; when B:NB 1, activity is diminished; and when B:N= 1, there is no change in activity during cooling.…”

“…With these recent advances, broader animal use, and implementation of the technique in a growing number of laboratories it seemed appropriate to provide a thorough description of assembly, implantation procedures, maintenance and use of the cryoloop. The cryoloop method can be applied to assess cortical operations using, with equal success, behavioral or electrophysiological assays of neural operations (Horel, 1984(Horel, , 1992(Horel, , 1996Horel et al 1984Horel et al , 1987Payne et al, 1991Payne et al, , 1996aLomber et al, 1994Lomber et al, , 1996aLomber and Payne, 1996;Girard et al 1997;Hupé et al, 1998).…”