Jean-Pierre Richard

Sound analysis and synthesis using an Amiga micro-computer

ABSTRACT This note presents a program for analysis and synthesis of sounds designed to be used with an Amiga micro-computer. The user is in real-time control of the capture of the signal with reference to both time and amplitude parameters. Subsequently the chosen signal can be edited and analysed. Sonograms can be obtained at three resolutions, both in time and frequency. Measurements of time can be made on the signal, of frequency on the sonogram and of amplitude on sections. Three functions for the extraction of the fundamental are available. A synthetic sound may be obtained, either by modifying the amplitude and frequency modulation of an existing sound, or by creating a new sound by additive synthesis. All the commands can be selected by using a mouse, and the program is user-friendly.

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.

Functional organization of the forebrain auditory centres of the European starling: A study based on natural sounds

The field L complex is thought to be the highest auditory centre and the input in the song vocal nuclei. Different anatomical and functional subdivisions have been described in field L. Auditory neurons of field L are well activated by natural sounds and especially by species-specific sounds. A complex sound coding appears to exist in field L. However, until now, the spatial organization of the different functional subdivisions has been described only using artificial sounds. Here, we investigated the spatial distribution of neuronal responses in field L to species-specific songs. Starlings seemed to be a very appropriate species for this investigation, both because of their complex vocal behaviour that implies different levels of categorization and their neuronal responses towards complex song elements. Multi-unit recordings were performed in wild starlings that were awake. The method of backward correlation was used to visualize the functional organization and we represented the neuronal responses as both activity maps and correlation maps. The use of natural sounds allowed us to define several functional sub-areas with different neuronal processing. These results show that field L is involved in a more complex task than simple frequency processing.

Linking social and vocal brains: could social segregation prevent a proper development of a central auditory area in a female songbird?

Direct social contact and social interaction affect speech development in human infants and are required in order to maintain perceptual abilities; however the processes involved are still poorly known. In the present study, we tested the hypothesis that social segregation during development would prevent the proper development of a central auditory area, using a “classical” animal model of vocal development, a songbird. Based on our knowledge of European starling, we raised young female starlings with peers and only adult male tutors. This ensured that female would show neither social bond with nor vocal copying from males. Electrophysiological recordings performed when these females were adult revealed perceptual abnormalities: they presented a larger auditory area, a lower proportion of specialized neurons and a larger proportion of generalist sites than wild-caught females, whereas these characteristics were similar to those observed in socially deprived (physically separated) females. These results confirmed and added to earlier results for males, suggesting that the degree of perceptual deficiency reflects the degree of social separation. To our knowledge, this report constitutes the first evidence that social segregation can, as much as physical separation, alter the development of a central auditory area.

A new methodological approach to context analysis of call production

ABSTRACT There is a need to improve the assessment of causes and consequences of vocal behaviour. The lack of descriptions of the context of call or song production comes from the complexity of its definition. The context is composed of numerous physical and social parameters and therefore its analysis should be multi-dimensional. Classical approaches involve a relatively subjective data reduction. This is due to a pre-selection of the parameters which may be potentially involved, as the analysis becomes rapidly complicated when the number of factors increases. This paper describes a helpful method that allows a much wider range of potential parameters to be explored and displayed visually. The parameters selected for subsequent analysis are those indicated by the display as most relevant and are therefore not arbitrary. We applied this method to observations of events (external or internal to the group) or behaviours (including postures) preceding and following call production. Calls of Campbells monkeys Cercopithecus campbelli present call types composed of several stereotyped sub-types, raising the question of whether or not such variations have a functional meaning for animals. We present three examples of the application of this method to describe in detail the context of production of a given call type, to detect specific temporal sequences of production and to discriminate between structurally close sub-types.

New insights into the auditory processing of communicative signals in the HVC of awake songbirds.

In the present study, using a systematic recording method and a variety of stimuli, we determined the proportion of responsive sites and their response features in the vocal control nucleus HVC of awake-restrained starlings, a species with multiple song types. Responsive sites were classified into three groups, according to the number of stimuli to which they responded. Sites in the three groups showed responses to individual-specific songs, with sites in the group that showed responses to only one stimulus responding mostly to a birds own song. In comparison, very few sites exhibited responses to universal species-specific songs and to artificial nonspecific sounds. By contrast, data obtained in the same birds under urethane anesthesia show that, although the total proportion of responsive sites was similar, numerous responses to a universal species-specific song and to an artificial nonspecific pure tone could be observed.

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.

Ontogeny of the ultradian rhythm of activity in Japanese quail.

As soon as they hatch, gallinaceous chicks follow broody hens. This matriarchal unit presents a temporal organization of activity. The ontogeny of this ultradian rhythm of activity was followed in Japanese quail during their first 3 weeks of life. Under controlled laboratory conditions, 12 groups of four chicks were recorded using an activity monitoring system. They were observed between the ages of 2 and 17 days. Chicks in groups presented an ultradian rhythm of activity, with a period that increased significantly from 14.3 ± 1.4 minutes when chicks were 2 days old to 26.0 ± 1.9 minutes when they were 16 days old. The increase of ultradian periodicity was particularly pronounced during their first and third weeks of life. Finally, the ultradian period was correlated positively with body weight of the chicks. (Chronobiology International, 17(6), 767–776, 2000)

A rapid correlation method for the analysis of spectro-temporal receptive fields of auditory neurons

The evaluation of spectro-temporal receptive fields in auditory neurons makes use of a correlation technique that needs a high amount of calculation time. We present a method in which 2-ms time bins of post-stimulus time histograms, rather than every action potential, are the basis for correlation with the acoustic spectrum of the stimulus. In a t test the content of each bin is classified as excitatory, inhibitory or responseless. The bin width is adjusted to the temporal resolution of the units as determined in a gap detection analysis. The method presented here saves a substantial amount of analysis time and reveals adequately spectro-temporal receptive fields.

A QUANTITATIVE ANALYSIS OF INDIVIDUALITY IN BARNACLE GOOSE LOUD CALLS

ABSTRACT Barnacle goose loud calls were recorded in a semi-captive flock in Slimbridge. A q uantitati ve analysis of those calls revealed a high degree of individuality in their structure. The duration and fundamental frequency of the calls did not vary much between birds, but the frequency of maximum amplitude did vary from one bird to another. No differences appeared between sexes. Individuality involved complex parameters that required special analysis programs. Frequency spectrum and frequency modulation (obtained by fundamental extraction) were individually distinctive. The combination of these two parameters gives excellent individual distinctiveness and enables 98% correct identification of the calls of individuals.