Ultra-rapid categorisation in non-human primates
The visual system of primates is remarkably efficient for analysing information about objects present in complex natural scenes. Recent work has demonstrated that they perform this at very high speeds. In a choice saccade task, human subjects can initiate a first reliable saccadic eye movement response to a target (the image containing an animal) in only 120 ms after image onset. Such fast responses impose severe time constraints if one considers neuronal responses latencies in high-level ventral areas of the macaque monkey. The question then arises: are non-human primates able to perform the task? Two rhesus macaque monkeys (Macaca mulatta) were trained to perform the same forced-choice categorization task as the one used in humans. Both animals performed the task with a high accuracy and generalized to new stimuli that were introduced everyday: accuracy levels were comparable both with new and well-known images (84% vs. 94%). More importantly, reaction times were extremely fast (minimum reaction time 100 ms and median reaction time 152 ms). Given that typical single units onset times in Inferotemporal cortex (IT) are about as long as the shortest behavioural responses measured here, we conclude that visual processing involved in ultra rapid categorisations might be based on rather simple shape cue analysis that can be achieved in areas such as extrastriate cortical area V4. The present paper demonstrates for the first time, that rhesus macaque monkeys (Macaca mulatta) are able to match human performance in a forced-choice saccadic categorisation task of animals in natural scenes.
KeywordsReaction time Saccades Rhesus macaque monkey Categorisation Natural scenes
- Delorme A (2000) Traitement visuel rapide de scènes naturelles chez le singe, l’homme et la machine: une vision qui va de l’avant ... In. Paul Sabatier - Toulouse 3, Toulouse, p 314Google Scholar
- Nowak LG, Bullier J (1997) The timing of information transfer in the visual system. In: Rockland KS, Kaas JH, Peters A (eds) Extrastriate visual cortex in primates, vol 12. Plenum Press, New York, pp 205–241Google Scholar
- Van Essen DC (2005) Surface-Based Comparisons of Macaque and Human Cortical Organization. In: Dehaene S, Duhamel JR, Hauser MD, Rizzolatti G (eds) From monkey brain to human brain. A Fyssen Foundation Symposium, pp 3–20Google Scholar