GABA-induced inactivation of Cebus apella V2 neurons: effects on orientation tuning and direction selectivity

• Main Authors: A.K. Jansen-Amorim, M. Fiorani, R. Gattass
• Format: Article
• Language: English
• Published: Associação Brasileira de Divulgação Científica 2013-08-01
• Series: Brazilian Journal of Medical and Biological Research
• Subjects: Visual cortex; Single units; Extracellular recordings; New World monkeys
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2013000700589&lng=en&tlng=en

We investigated the GABA-induced inactivation of V2 neurons and terminals on the receptive field properties of this area in an anesthetized and paralyzed Cebus apella monkey. Extracellular single-unit activity was recorded using tungsten microelectrodes in a monkey before and after pressure-injection of a 0.25 or 0.5 M GABA solution. The visual stimulus consisted of a bar moving in 8 possible directions. In total, 24 V2 neurons were studied before and after blocker injections in 4 experimental sessions following GABA injection into area V2. A group of 10 neurons were studied over a short period. An additional 6 neurons were investigated over a long period after the GABA injection. A third group of 8 neurons were studied over a very long period. Overall, these 24 neurons displayed an early (1-20 min) significant general decrease in excitability with concomitant changes in orientation or direction selectivity. GABA inactivation in area V2 produced robust inhibition in 80% and a significant change in directional selectivity in 60% of the neurons examined. These GABA projections are capable of modulating not only levels of spontaneous and driven activity of V2 neurons but also receptive field properties such as direction selectivity.