A songbird forebrain area potentially involved in auditory discrimination and memory formation

Abstract

Songbirds rely on auditory processing of natural communication signals for a number of social behaviors,including mate selection,individual recognition and the rare behavior of vocal learning - the ability to learn vocalizations through imitation of an adult model,rather than by instinct. Like mammals,songbirds possess a set of interconnected ascending and descending auditory brain pathways that process acoustic information and that are presumably involved in the perceptual processing of vocal communication signals. Most auditory areas studied to date are located in the caudomedial forebrain of the songbird and include the thalamo-recipient field L (sub fields L1,L2 and L3),the caudomedial and caudolateral mesopallium (CMM and CLM,respectively) and the caudomedial nidopallium (NCM). This review focuses on NCM,an auditory area previously proposed to be analogous to parts of the primary auditory cortex in mammals. Stimulation of songbirds with auditory stimuli drives vigorous electrophysiological responses and the expression of several activity-regulated genes in NCM.Interestingly,NCM neurons are tuned to species-specific songs and undergo some forms of experience-dependent plasticity in-vivo . These activity-dependent changes may underlie long-term modifications in the functional performance of NCM and constitute a potential neural substrate for auditory discrimination. We end this review by discussing evidence that suggests that NCM may be a site of auditory memory formation and/or storage.

Estradiol Shapes Auditory Processing in the Adult Brain by Regulating Inhibitory Transmission and Plasticity-Associated Gene Expression

“…In fact, auditory experience drives the expression of activity-dependent genes in NCM, most of which are regulated by the MAPK pathway, including the IEGs zenk, c-fos, and arc (Cheng and Clayton, 2004;Velho et al, 2005;Pinaud et al, 2008a). Activation of the MAPK pathway in NCM is required for the formation of auditory memories necessary for vocal learning (London and Clayton, 2008) and is thought to represent a central event in the cascade of cellular processes leading to neuronal plasticity associated with auditory learning and, perhaps, memory formation in the adult NCM Velho et al, 2005;Mello and Pinaud, 2006;Pinaud and Terleph, 2008). Importantly, research conducted in other preparations indicates that E2 may directly modulate the activity of the MAPK pathway, raising the possibility that auditory-driven gene expression in NCM may be regulated by local E2 levels (McEwen and Alves, 1999;Mannella and Brinton, 2006;Jover-Mengual et al, 2007).…”

“…The caudomedial nidopallium (NCM), a forebrain area thought to be analogous to the mammalian auditory association cortex (Vates et al, 1996;Mello et al, 2004;Bolhuis and Gahr, 2006;Pinaud and Terleph, 2008), contains neurons that are selective to speciesspecific songs (Mello et al, 1992;Chew et al, 1996;Stripling et al, 2001). NCM neurons also undergo stimulus-specific adaptation of neurophysiological and genomic responses; such changes are long lasting and may support auditory discrimination and song recognition memories (Chew et al, 1995;Mello et al, 1995).…”

The ecological relevance of sleep: the trade-off between sleep, memory and energy conservation

“…The processing, transfer and storage of memories in birds are even less well known than in mammals. There is some evidence that caudomedial nidopallium plays an important role in the long-term storage of song memories produced elsewhere in the song-control system (Pinaud & Terleph 2008), but the evidence for a similar pattern involving the hippocampus is equivocal. Avian song learning paths are independent of the hippocampus and are uniquely avian (Clayton & Soha 1999), so this pattern may or may not exist.…”

Topography of estradiol‐modulated genomic responses in the songbird auditory forebrain

“…This large and complex region is analogous to the supragranular layers of mammalian auditory cortex and plays important roles in perceptual processing and auditory learning (reviewed by Mello, 2004;Pinaud and Terleph, 2008). The majority of research on song-induced activity in NCM has focused on the genomic response, or the expression of immediate early genes such as zenk (egr-1).…”