Functional changes between seasons in the male songbird auditory forebrain

Abstract

Songbirds are an excellent model for investigating the perception of learned complex acoustic communication signals. Male European starlings (Sturnus vulgaris) sing throughout the year distinct types of song that bear either social or individual information. Although the relative importance of social and individual information changes seasonally, evidence of functional seasonal changes in neural response to these songs remains elusive. We thus decided to use in vivo functional magnetic resonance imaging (fMRI) to examine auditory responses of male starlings that were exposed to songs that convey different levels of information (species-specific and group identity or individual identity), both during (when mate recognition is particularly important) and outside the breeding season (when group recognition is particularly important). We report three main findings: (1) the auditory area caudomedial nidopallium (NCM), an auditory region that is analogous to the mammalian auditory cortex, is clearly involved in the processing/categorization of conspecific songs; (2) season-related change in differential song processing is limited to a caudal part of NCM; in the more rostral parts, songs bearing individual information induce higher BOLD responses than songs bearing species and group information, regardless of the season; (3) the differentiation between songs bearing species and group information and songs bearing individual information seems to be biased toward the right hemisphere. This study provides evidence that auditory processing of behaviorally-relevant (conspecific) communication signals changes seasonally, even when the spectro-temporal properties of these signals do not change.

A novel statistical method for behaviour sequence analysis and its application to birdsong

“…It has also been proposed that distinct categories of whistles convey meaning about species or individual identity (Hausberger, 1997; Henry et al, 1994); however, we did not attempt to distinguish among distinct whistle types in the present study. Consistent with a role for at least some whistle types in mate attraction, an auditory-processing region in the female brain is more responsive (measured using fMRI activity) to species-specific male whistle types during the breeding season (De Groof, Poirier, George, Hausberger, & Van der Linden, 2013). Future studies in which distinct whistle types are categorized and the influence of breeding condition versus pairing status are needed to further understand this phrase category.…”

Anesthesia and brain sensory processing: impact on neuronal responses in a female songbird

“…Maybe anesthesia may affect “attention units” such as those described in cats, which respond to sounds only if they are associated with some attentional focus of the subject26. Interestingly, there might be sexual differences in the effects of anesthesia on seasonal plasticity: female white crowned sparrows are affected by anesthesia but not males23 while male starlings are affected but not females27. Further studies are clearly needed to understand the relationship between anesthesia, brain adult plasticity and sex.…”

Neuroplasticity and MRI: A perfect match

“…the volume and interconnectivity between distinct song control system components dramatically increases in anticipation of the breeding season, preparing birds to sing. Interestingly, this photoperioddriven change in hormone levels directly affects overall anatomy including the brain, but also drives singing behavior (Tramontin and Brenowitz 2000) and affects auditory perception of song (De Groof, Poirier et al 2013). In addition, most seasonal species are capable of adapting and extending their song repertoire on a yearly basis.…”