Abstract
Although neural responses to sound stimuli have been thoroughly investigated in various areas of the auditory cortex, the results electrophysiological recordings cannot establish a causal link between neural activation and brain function. Electrical microstimulation, which can selectively perturb neural activity in specific parts of the nervous system, is an important tool for exploring the organization and function of brain circuitry. To date, the studies describing the behavioral effects of electrical stimulation have largely been conducted in the primary auditory cortex. In this study, to investigate the potential differences in the effects of electrical stimulation on different cortical areas, we measured the behavioral performance of cats in detecting intra-cortical microstimulation (ICMS) delivered in the primary and secondary auditory fields (A1 and A2, respectively). After being trained to perform a Go/No-Go task cued by sounds, we found that cats could also learn to perform the task cued by ICMS; furthermore, the detection of the ICMS was similarly sensitive in A1 and A2. Presenting wideband noise together with ICMS substantially decreased the performance of cats in detecting ICMS in A1 and A2, consistent with a noise masking effect on the sensation elicited by the ICMS. In contrast, presenting ICMS with pure-tones in the spectral receptive field of the electrode-implanted cortical site reduced ICMS detection performance in A1 but not A2. Therefore, activation of A1 and A2 neurons may produce different qualities of sensation. Overall, our study revealed that ICMS-induced neural activity could be easily integrated into an animal’s behavioral decision process and had an implication for the development of cortical auditory prosthetics.
Highlights
It has been well established that the auditory cerebral cortex is subdivided into a primary area (A1) and multiple non-primary areas (Read et al, 2002; Winer and Lee, 2007; Hackett et al, 2014)
The order of the stimulation site was counterbalanced across animals: A1 A2 for half the Experiment 1: Detection of intra-cortical microstimulation (ICMS) in A1 and A2 The Go responses to ICMS in A1 and A2 are presented in Figures 2A,B, respectively
For a comparison of data from different brain areas, we constructed a psychometric function by plotting the percentage of correct detection against pulse amplitude (Figure 2C)
Summary
It has been well established that the auditory cerebral cortex is subdivided into a primary area (A1) and multiple non-primary areas (Read et al, 2002; Winer and Lee, 2007; Hackett et al, 2014). Previous electrophysiological research has demonstrated the response properties of neurons subjected to various sound stimuli in these areas and has yielded a greater understanding of auditory cortical circuitry. As an alternative to sound stimulation, electrical microstimulation can be used to better understand the brain’s natural circuitry by perturbing the circuitry to generate percepts (Stanley, 2013). Several previous studies have shown that animals can detect a focal stimulation of A1 with a weak electric current (intra-cortical microstimulation or ICMS; Otto et al, 2005; Deliano et al, 2009; Wang et al, 2012). The effects of ICMS have primarily been studied in A1 of animals; the effects of ICMS on the nonprimary auditory areas remain largely unknown
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