A novel coding mechanism for social vocalizations in the lateral amygdala

Abstract

The amygdala plays a central role in evaluating the significance of acoustic signals and coordinating the appropriate behavioral responses. To understand how amygdalar responses modulate auditory processing and drive emotional expression, we assessed how neurons respond to and encode information that is carried within complex acoustic stimuli. We characterized responses of single neurons in the lateral nucleus of the amygdala to social vocalizations and synthetic acoustic stimuli in awake big brown bats. Neurons typically responded to most of the social vocalizations presented (mean = nine of 11 vocalizations) but differentially modulated both firing rate and response duration. Surprisingly, response duration provided substantially more information about vocalizations than did spike rate. In most neurons, variation in response duration depended, in part, on persistent excitatory discharge that extended beyond stimulus duration. Information in persistent firing duration was significantly greater than in spike rate, and the majority of neurons displayed more information in persistent firing, which was more likely to be observed in response to aggressive vocalizations (64%) than appeasement vocalizations (25%), suggesting that persistent firing may relate to the behavioral context of vocalizations. These findings suggest that the amygdala uses a novel coding strategy for discriminating among vocalizations and underscore the importance of persistent firing in the general functioning of the amygdala.

Processing of Communication Calls in Guinea Pig Auditory Cortex

“…Auditory areas with a greater involvement in processing communication calls may show one or more of the following characteristics: (1) they may contain a greater proportion of cells that respond preferentially to communication calls over simple stimuli [13], [14], (2) they may contain many highly selective cells that only respond to one or very few out of a range of calls [15], [14], (3) they may contain a high proportion of discriminatory cells that respond to many calls but differentiate among them in their response patterns either by using a temporal code [16], [17] or (4) a rate code [18]. Finally, cortical areas may have other ways of representing information about a call [19], and they may use either a sparse or a dense representation [20].…”

Social Isolation During Postweaning Development Causes Hypoactivity of Neurons in the Medial Nucleus of the Male Rat Amygdala

“…MeA receives excitatory glutamatergic inputs from several regions, including the LAT (Pitkanen et al, 1995). LAT was chosen for stimulation because its output is glutamatergic (McDonald, 1996) and it has functional importance in guidance of affective behavior, including some social behaviors (Hoffman et al, 2007;Davis et al, 2010;Jeon et al, 2010;Gadziola et al, 2012). LAT stimulation evoked a stimulation intensity-dependent local field potential in the MeA (Figure 1d; slope of the local field potential across intensity, main effect of intensity po0.0001, F(4,124) = 360.4, two-way RM-ANOVA).…”

Subcortical processing in auditory communication

“…Evidence in this direction comes from animal and human observations. In bats, single neuron recordings from the lateral nucleus of the amygdala have reported selective responsiveness in terms of persistent firing to social vocalisations, especially of negative valence (Gadziola et al, 2012). This persistent firing, which can be reduced by manipulating the spectrotemporal features of the stimuli, and enhanced by chemically activating the MGB (Peterson and Wenstrup, 2012), is a recurrent finding, and is considered a distinctive feature of amygdalar responses to social vocalisations.…”