Slow Modulation of Ongoing Discharge in the Auditory Cortex during an Interval-Discrimination Task

Juan M Abolafia,Marina Martinez-Garcia,Gustavo Deco,Maria V Sanchez-Vives

doi:10.3389/fnint.2011.00060

Abstract

In this study, we recorded single unit activity from rat auditory cortex while the animals performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms, and go to the left or right nose poke accordingly. Spontaneous firing in between auditory responses was compared in the attentive versus non-attentive brain states. We describe the firing rate modulation detected during intervals while there was no auditory stimulation. Nearly 18% of neurons (n = 14) showed a prominent neuronal discharge during the interstimulus interval, in the form of an upward or downward ramp towards the second auditory stimulus. These patterns of spontaneous activity were often modulated in the attentive versus passive trials. Modulation of the spontaneous firing rate during the task was observed not only between auditory stimuli, but also in the interval preceding the stimulus. These slow modulatory components could be locally generated or the result of a top-down influence originated in higher associative association areas. Such a neuronal discharge may be related to the computation of the interval time and contribute to the perception of the auditory stimulus.

Highlights

Sensory areas such as primary auditory cortex are primarily associated with stimulus encoding and there are different aspects of neuronal responses relevant to this function
We recorded from neurons from the rat primary auditory cortex while the animal was performing an interval-discrimination task
We report about 14 particular neurons that showed prominent responses during the intervals between stimuli, with firing rates that either increased or decreased toward the second stimulus. These neuronal discharges could be refered to as spontaneous activity, since they occurred while there was no auditory stimulation

Summary

Introduction

Sensory areas such as primary auditory cortex are primarily associated with stimulus encoding and there are different aspects of neuronal responses relevant to this function. Slow modulation of sustained responses has been found to predict the behavioral decisions during auditory categorization tasks in monkeys, including errors (Selezneva et al, 2006). Slow modulation of firing could constitute an anticipatory mechanism that associates events (stimulus–behavior–reinforcer) that are relevant or adaptive to the environment. These cognitive components associated to stimulus discrimination tasks have been more commonly associated to higher areas such as frontal areas (Romanski and Goldman-Rakic, 2002; Lemus et al, 2009)

Methods

Results

Conclusion