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Biomedical subjects

D Symmes

Publications and source records attributed to D Symmes.

At least 19 recordsLinked to original sources
PubMed1989

Contour variables in vocal communication between squirrel monkey mothers and infants.

This study investigates the occurrence and structure of the caregiver call, a form of communication in squirrel monkeys that is almost exclusively infant-directed. Caregiver calls exhibit variability in several acoustic features, most notably pitch range and contour, which are significantly associated with particular contexts of infant care; e.g., nursing or retrieval. The use of caregiver calls by squirrel monkeys is compared to the use of motherese (infant-directed speech) by humans. The possible functional and motivational basis for specific acoustic variables in the caregiver call is discussed.

Animals↗
PubMed1986

Play vocalizations of squirrel monkeys (Saimiri sciureus).

Vocalizations occurring during play bouts were studied in 2 pairs of young male squirrel monkeys. Two main call types, one having four variants, are described. Vocalization rate varied with the type of ongoing behavior and with play bout duration, an association considered to be indicative of motivation to play. Structural differences also varied with bout duration and longer bouts had longer and more complex calls. In addition to providing direct information about motivation, vocalizations may have a metacommunicative function in alerting adult group members (not play partners) to the presence of playful activity.

Animals↗
PubMed1985

Patterns of inhibition in auditory cortical cells in awake squirrel monkeys.

Two-tone interactions are recorded in the responses of single units in the superior temporal gyrus to contralateral acoustic stimulation of the awake squirrel monkey. Four response types are distinguished based primarily on the nature of the inhibitory responses elicited by two-tone stimuli, and secondarily on such criteria as the patterns of response to single tones and noise stimuli, thresholds, and spontaneous activity levels. Type A units display strong lateral inhibitory influences which may extend up to 2 octaves on either side, or both sides, of the BF. They are sharply tuned at all intensities and exhibit sustained response to single tone stimuli at the BF. The units have nonmonotonic rate-level functions, and show little or no response to broad band noise. Type A units have low spontaneous rates (less than 3 spikes/s) and relatively high thresholds (greater than or equal to 30 dB SPL). Type B units are characterized by relatively high spontaneous rates of activity (greater than 20 spikes/s) and inhibitory responses to single tone stimuli. Broad band noise may evoke strong excitatory response. Type C units summate the responses to the two-tone stimulus, and show little or no inhibitory influences. They have V-shaped tuning curves, monotonic rate-level functions, low thresholds (greater than or equal to 30 dB SPL), moderate spontaneous rates (ca. 10 spikes/s), and a strong and sustained response to noise and single tone stimuli. Type D units show 'temporal inhibition' to two-tone stimuli, in that an excitatory response to the first tone suppresses (adapts or inhibits) the response to the second tone. These units generally have moderate to broad frequency tuning and phasic responses to single tone stimuli. Histological examination of electrode tracks suggests that Type A units are restricted to A1 (and possibly the rostral field) while other types are distributed over all auditory fields.

Acoustic Stimulation↗
PubMed1983

Effects of reproductive state on vocalizations in squirrel monkeys (Saimiri sciureus).

Vocalizations and behavior of a group of 6 squirrel monkeys, 2 males and 4 females, were recorded during the nonbreeding and breeding seasons. Behavioral and physical criteria were used to determine the presence of estrus. During the breeding season the types of vocalizations uttered by estrous females changed, and the adult male increased his rate of vocalizing. Err vocalizations by estrous females were associated with increased following and initiation of affiliative behavior with the adult male, and may have functioned to facilitate these interactions. Errs appeared to be related to changes in female reproductive state rather than to the behavior of others. The adult male increased vocalizations associated with sexual and aggressive behavior (squeals and cackles), primarily in response to the estrous females' persistent initiation of interactions with him. We concluded that certain vocalizations in Saimiri reflected changes in the reproductive state of males and females, and functioned to mediate changes in social bonding during the breeding season.

Animals↗
PubMed1981

On the use of natural stimuli in neurophysiological studies of audition.

Close scrutiny of the conceptual base which supports a recent explosion of interest in biologically relevant stimuli reveals several gaps and examples of inconsistent terminology. It is apparent that selection of stimuli has not always been optimal, in the sense that relevance was undefined and controls were lacking. The neurophysiological evidence most often sought has been the response of single neurons in central auditory pathways, and presentation of these results has at times made progress difficult to discern. A simplified, testable version of the feature detector hypothesis is discussed.

Acoustic Stimulation↗
PubMed1980

Neural processing of vocalizations and artificial stimuli in the medial geniculate body of squirrel monkey.

The responses of 256 single neurons in the medial geniculate body of awake squirrel monkeys have been examined with a variety of acoustic stimuli. Both traditional artificial sounds and tape-recorded tokens of species-specific vocalizations were employed, and one goal of the study was the comparison along a number of response parameters of these two classes. Unit responses to the first group (clicks, tone bursts and noise bursts) revealed a level of responsivity approaching 100% in the principal nucleus. Responses to tone and noise were sustained in about half the cells, and characteristic frequencies could be identified in 81%. Responses to vocal stimuli were also very prevalent, approaching 100% in this sample. A comparison of absolute thresholds, response vigor, rate-level functions, binaural interactions, and spectral composition of effective stimuli confirmed that MGB cells process vocal stimuli and artificial stimuli in similar ways. Selectivity of MGB cells to vocal stimuli was quite low, suggesting that processing of communication sounds in MGB is relatively simple and preliminary when compared to auditory cortex.

Acoustic Stimulation↗