Ranulfo Romo has continued to carry out a series of experiments examining the neural basis of flutter discrimination, building upon classic studies of Mountcastle. Recently, he has moved his studies to examining auditory flutter discrimination, where he has examined the neural mechanisms underlying the ability to discriminate between two successively presented auditory flutter stimuli. This Wednesday, at Sensorimotor Journal Club, Sri Nagarajan will present a recent paper where Romo demonstrates that in a two-interval forced choice paradigm (2IFC), ventral premotor cortex is active during the period between two stimuli - in the working memory and decision making periods. These results can be interpreted in the context of a state-estimation with an internal model, but Romo prefers a more traditional computational view. The paper Sri will present is:

 

Lemus, L., Hernandez, A., & Romo, R. (2009). Neural encoding of auditory discrimination in ventral premotor cortex. Proceedings of the National Academy of Sciences, 106(34), 14640-14645. (link to pdf of article)

 

Monkeys have the capacity to accurately discriminate the difference between two acoustic flutter stimuli. In this task, monkeys must compare information about the second stimulus to the memory trace of the first stimulus, and must postpone the decision report until a sensory cue triggers the beginning of the decision motor report. The neuronal processes associated with the different components of this task have been investigated in the primary auditory cortex (A1); but, A1 seems exclusively associated with the sensory and not with the working memory and decision components of this task. Here, we show that ventral premotor cortex (VPC) neurons reflect in their activities the current and remembered acoustic stimulus, their comparison, and the result of the animal's decision report. These results provide evidence that the neural dynamics of VPC is involved in the processing steps that link sensation and decision-making during auditory discrimination.