Biomedical subjects

Hugo Cousillas

Publications and source records attributed to Hugo Cousillas.

8 recordsLinked to original sources

PubMed2006

Social experience influences the development of a central auditory area.

Vocal communication develops under social influences that can enhance attention, an important factor in memory formation and perceptual tuning. In songbirds, social conditions can delay sensitive periods of development, overcome learning inhibitions and enable exceptional learning or induce selective learning. However, we do not know how social conditions influence auditory processing in the brain. In the present study, we raised young naive starlings under different social conditions but with the same auditory experience of adult songs, and we compared the effects of these different conditions on the development of the auditory cortex analogue. Several features appeared to be influenced by the social experience, among which the proportion of auditory neuronal sites and the neuronal selectivity. Both physical and social isolation from adult models altered the development of the auditory area in parallel to alterations in vocal development. To our knowledge, this is the first evidence that social deprivation has as much influence on neuronal responsiveness as sensory deprivation.

Animals↗

PubMed2005

State-dependent hemispheric specialization in the songbird brain.

Lateralization of brain functions is a widespread phenomenon in vertebrates. With the well-known lateralization in the processing of human speech and the parallels that exist between birdsong and language, songbirds are interesting for addressing such questions. In the present study, we investigated the central processing of communicative and artificial sounds in starlings, in an integrative part of the song system: the HVC. Neuronal responses to acoustic stimuli were systematically recorded in both hemispheres while the birds were awake, and then anesthetized, allowing quantitative comparisons of the responses obtained in each situation. The total proportion of responsive sites in the HVC of the left and right hemispheres of all birds revealed a significant predominance of the HVC of the right hemisphere when the birds were awake, whereas a high interindividual variability appeared when the birds were anesthetized. When neuronal responses as a whole were further examined, the responses to each type of stimulus appeared to be nonrandomly distributed over the different situations, and some specialization may appear. The results suggest a complex and state-dependent hemispheric specialization toward behaviorally relevant classes of stimuli. In awake birds, the HVC of the left hemisphere may be more involved in the processing of songs that are used in individual recognition at distance, whereas the HVC of the right hemisphere may deal with long and complex sequences of a song that is involved in short-distance communication, especially between males and females. With birds under anesthesia, this pattern is strongly modified.

Animal Communication↗

PubMed2005

Auditory responses in the HVC of anesthetized starlings.

The present study, using a systematic recording method that we recently developed, describes the behavior of the neurons of the vocal control nucleus HVC in response to a variety of acoustic stimuli in a songbird species with multiple song types, the European starling. Most neurons did not respond to any of the stimuli that were presented, and those neurons that did respond responded to a different number of stimuli and showed distinct response features. The latter were thus classified into 3 categories, according to the number of stimuli to which they responded. Although only intracellular data could unambiguously determine to which population the neurons we recorded belonged, these 3 categories might correspond to the 3 populations of neurons that have been previously described in the HVC. Interestingly, responsive neurons of the 3 categories appeared to mainly respond to stimuli that were not the bird's own song. However, most of the stimuli to which the HVC neurons responded correspond to sounds that are important in the everyday social life of the starlings. We thus discuss our results in relation to the social life of these birds, to possible species differences in the processing of communicative signals, and to methodological issues.

Acoustic Stimulation↗

PubMed2004

Direct social contacts override auditory information in the song-learning process in starlings (Sturnus vulgaris).

Social influence on song acquisition was studied in 3 groups of young European starlings raised under different social conditions but with the same auditory experience of adult song. Attentional focusing on preferred partners appears the most likely explanation for differences found in song acquisition in relation to experience, sex, and song categories. Thus, pair-isolated birds learned from each other and not from broadcast live songs, females did not learn from the adult male tutors, and sharing occurred more between socially associated peers. On the contrary, single-isolated birds clearly copied the adult songs that may have been the only source of attention stimulation. Therefore, social preference appears as both a motor for song learning and a potential obstacle for acquisition from nonpreferred partners, including adults.

Animals↗

PubMed2004

Hemispheric specialization in the primary auditory area of awake and anesthetized starlings (Sturnus vulgaris).

Although evidence exists for a lateralization of song production, few studies have focused on the perceptual aspect of lateralization in songbirds. In the present study, the authors recorded neuronal responses to a variety of species-specific and artificial, nonspecific stimuli in both hemispheres of awake and anesthetized male starlings (Sturnus vulgaris). Recordings were made in the primary auditory area of the songbird brain, the Field L complex. The right hemisphere exhibited significantly more responsive units than the left hemisphere in awake birds, and this difference was significantly reduced in anesthetized birds. Furthermore, clear hemispheric specialization toward categories of behaviorally relevant stimuli and precise parameters of these stimuli were found. The main auditory area of the starling's brain thus appears to show some degree of lateralization.

Acoustic Stimulation↗

PubMed2004

Experience-dependent neuronal specialization and functional organization in the central auditory area of a songbird.

The effect of early experience on brain development was investigated in the central auditory area of a songbird, the field L complex, which is analogous to the mammalian auditory cortex. Multi-unit recordings of auditory responses in the field L complex of adult starlings raised without any experience of adult song during development provide strong evidence of developmental plasticity both in the neuronal responses and in the functional organization of this area. Across the entire area, experimental birds, separated from adults from the age of 1 week old until they were 2 years old, had a much larger number of neurons that responded to all the stimuli than did control birds. The well-known tonotopy demonstrated in adult wild birds using the same procedure was altered. This study is the first to bring evidence of developmental plasticity in the organization of the central auditory areas in songbirds. These results are discussed in relation to other reports on effects of early experience on brain development.

Acoustic Stimulation↗

PubMed2003

A new extensive approach to single unit responses using multisite recording electrodes: application to the songbird brain.

One of the most challenging issues in neuroethology concerns the neural substrates for song production, perception and learning in songbirds. However, electrophysiological studies of the song system of songbirds are often fragmented and centered on a small number of selected neurons. Here, we have developed a new extensive approach to record a great number of single units in the brain of a songbird, the European starling. The aim of this approach is to formulate quantitative assumptions about the electrophysiological characteristics of the brain nucleus investigated: e.g. the proportion of auditory neurons, neuronal selectivity, etc. We applied a mapping method using multisite recording electrodes and online isolation of single-units, without preselecting neurons with a search stimulus. As an example of the application of this technique, we have mapped the responses to a variety of natural and artificial acoustic stimuli recorded systematically throughout the HVC of both awake and anaesthetized male starlings. This method appears to be powerful and allowed us to quantitatively compare responses obtained in awake and anaesthetized birds by recording over 1000 single units. We think that, in future, this will enable us to characterize and compare parts of nuclei or entire nuclei and to better understand how the song system works.

Acoustic Stimulation↗

PubMed2002

Song perception in the European starling: hemispheric specialisation and individual variations.

Hemispheric specialisation for speech in humans has been well documented. The lateralisation for song production observed in songbirds is reminiscent of this hemispheric dominance. In order to investigate whether song perception is also lateralised, we made multiunit recordings of the neuronal activity in the field L of starlings during the presentation of species-specific and artificial non-specific sounds. We observed a systematic stronger activation in one hemisphere than in the other one during the playback of species-specific sounds, with inter-subject variability in the predominant hemisphere for song perception. Such an asymmetry was not observed for artificial non-specific sounds. Thus, our results suggest that, at least at the individual level, the two hemispheres of the starlings' brain perceive and process conspecific signals differently.

Acoustic Stimulation↗