Variability and information content in auditory cortex spike trains during an interval-discrimination task

Abstract

Abolafia JM, Martinez-Garcia M, Deco G, Sanchez-Vives MV. Variability and information content in auditory cortex spike trains during an interval-discrimination task. J Neurophysiol 110: 2163-2174, 2013. First published August 14, 2013 doi:10.1152/jn.00381.2013.-Processing of temporal information is key in auditory processing. In this study, we recorded single-unit activity from rat auditory cortex while they performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms and nose-poke to the left or to the right accordingly. The spike firing of single neurons in the auditory cortex was then compared in engaged vs. idle brain states. We found that spike firing variability measured with the Fano factor was markedly reduced, not only during stimulation, but also in between stimuli in engaged trials. We next explored if this decrease in variability was associated with an increased information encoding. Our information theory analysis revealed increased information content in auditory responses during engagement compared with idle states, in particular in the responses to task-relevant stimuli. Altogether, we demonstrate that task-engagement significantly modulates coding properties of auditory cortical neurons during an interval-discrimination task. auditory processing; firing modulation; auditory cortex A RELEVANT ASPECT OF AUDITORY perception is the analysis of temporal information. Different studies have shown how single units of auditory cortex discriminate relevant temporal information for behavior (Bao et al. 2004;Fritz et al. 2007;Lemus et al. 2009;Polley et al. 2006). Temporal processing in auditory cortex has been previously studied by means of a number of experimental manipulations. Some studies have focused on interval production tasks (Merchant et al. 2008), discrimination of stimuli repetition rate (Bao et al. 2004;Fritz et al. 2007;Lemus et al. 2009;Polley et al. 2006), or frequency categorization of tones (Ohl et al. 2001;Selezneva et al. 2006). However, the mechanisms of temporal discrimination at the level of the cortical single unit are not well known. This issue was explored in a recent study where monkeys had to compare two acoustic flutter stimuli (Lemus et al. 2009). In that study, an absence of modulation of neuronal firing related to working memory or to decision components of the task was found. We were interested to explore the task-modulation of neuronal discharges to identical stimulation patterns, in particular in a task where the interval between stimuli would be behaviorally relevant. For that purpose, we devised an interval-discrimination task where the same patterns of auditory stimulation were carried out during engaged (correct choices provided reward) and in idle states (performance not required), and studied spontaneous and evoked firing patterns of single auditory cortical neurons.Studies of neural mechanisms of auditory processing in auditory cortex have reported both an increased excitability and respons...

Representation of foreseeable choice outcomes in orbitofrontal cortex triplet-wise interactions

“…The functional role of the observed neural and behavioral variability in repetitions of the same task is a fundamental question in systems neuroscience [1][2][3][4][5][6][7][8][9][10][11][12][13] and is currently under extensive discussion. The focus has been mainly on the analysis of trial-to-trial variability dynamics in motor [2,[14][15][16][17] or in sensory [4,8,16,[18][19][20] cortical areas; and more recently in frontal regions during decision-making tasks [2,3,[21][22][23].…”

“…In this work, we investigate this scenario further by focusing on the relationship between optimal choice behavior and shared trial-to-trial variability in rodent OFC [20,41]. The OFC provides a particularly interesting case study, since it has been associated with multiple behaviorally relevant variables in the decision-making task space (e.g., [42][43][44][45][46][47][48][49][50][51]) such as outcomes expectations that guide action [41,52], their desirability [53] or the availability of multiple-valued choices in economic decision making [45] (but see also [54]).…”

Behavioral Context Determines Network State and Variability Dynamics in Monkey Motor Cortex

“…Davies et al ( 2006 ) showed that in motor cortex spike time irregularity increases during the most demanding epoch of a precision grip task. Spike count variability, on the other hand, systematically decreases during a behavioral task being lowest during movement execution (Churchland et al, 2006 , 2010 ; Rickert et al, 2009 ), perceptual processing (Mitchell et al, 2009 ; Churchland et al, 2010 ; Abolafia et al, 2013 ; Ponce-Alvarez et al, 2013 ; Mazzucato et al, 2015 ), attention (Mitchell et al, 2007 ; but see McAdams and Maunsell, 1999 ), or in relation to decision processes (Churchland et al, 2011 ). In addition, Rickert et al ( 2009 ) showed that during movement preparation and execution the FF in motor cortex depends on the amount of prior information about the requested movement.…”

Behavioral context determines network state and variability dynamics in monkey motor cortex

“…Davies et al (2006) showed that in motor cortex spike time irregularity increases during the most demanding epoch of a precision grip task. Spike count variability, on the other hand, systematically decreases during a behavioral task being lowest during movement execution (Churchland MM et al 2006, 2010Rickert et al 2009), perceptual processing (Mitchell et al 2009;Churchland MM et al 2010;Abolafia et al 2013;Ponce-Alvarez et al 2013;Mazzucato et al 2015), attention (Mitchell et al 2007; but see McAdams and Maunsell 1999), or in relation to decision processes (Churchland AK et al 2011). In addition, Rickert et al (2009) showed that during movement preparation and execution the FF in motor cortex depends on the amount of prior information about the requested movement.…”