TUNING PROPERTIES OF SPATIAL AND TEMPORAL CHANNELS OF VISION - CLINICAL CONSEQUENCES

Specificity of cells in the primary cortex of the cat has been studied for two parameters frequently clinically evaluated: spatial and tempo ral frequencies. Spatial and temporal characteristics of area 17 neuro ns have been studied through the analysis of peak frequencies and tuni ng curves. 172 cells from eight anesthetized adult cats were recorded with an extracellular approach. Spatial and temporal optimal frequenci es were assessed for each cell, as well as the bandwidth of tuning fun ctions. The mean tuning curve was 1.84 +/- 0.60 octaves (mean +/- SD) for spatial frequencies and 2.40 +/- 0.69 octaves for temporal frequen cies; this difference was highly significant (p<0.01). 12% of cells we re low-pass for spatial frequency and 33% for temporal frequencies. Th ere was no correlation between bandwidth for spatial and temporal para meters. These results indicate that spatial specificity is higher than temporal specificy in area 17 of the cat. In consequence, it appears that visual spatial channels are much more numerous than temporal ones . This could have some importance for clinical evaluation of spatial a nd temporal properties of vision. On the one hand, the lower specifici ty of temporal channels makes evaluation of motion perception more sen sitive to adaptation phenomena than spatial evaluation. On the other h and, this low specificity makes motion perception easier to assess, as there is no need to evaluate perception for a large number of tempora l frequencies.