Neural representation of face familiarity in an awake chimpanzee.

Evaluating the familiarity of faces is critical for social animals as it is the basis of individual recognition. In the present study, we examined how face familiarity is reflected in neural activities in our closest living relative, the chimpanzee. Skin-surface event-related brain potentials (ERPs) were measured while a fully awake chimpanzee observed photographs of familiar and unfamiliar chimpanzee faces (Experiment 1) and human faces (Experiment 2).

Brain response to affective pictures in the chimpanzee.

Advancement of non-invasive brain imaging techniques has allowed us to examine details of neural activities involved in affective processing in humans; however, no comparative data are available for chimpanzees, the closest living relatives of humans. In the present study, we measured event-related brain potentials in a fully awake adult chimpanzee as she looked at affective and neutral pictures. The results revealed a differential brain potential appearing 210 ms after presentation of an affective picture, a pattern similar to that in humans.

Event-related potentials in response to subjects' own names: A comparison between humans and a chimpanzee.

The sound of one's own name is one of the most salient auditory environmental stimuli. Several studies of human brain potentials have revealed some characteristic waveforms when we hear our own names. In a recent work, we investigated event-related potentials (ERPs) in a female chimpanzee and demonstrated that the ERP pattern generated when she heard her own name differed from that generated when she heard other sounds.

Neural correlates of face and object perception in an awake chimpanzee (Pan troglodytes) examined by scalp-surface event-related potentials.

Background: The neural system of our closest living relative, the chimpanzee, is a topic of increasing research interest. However, electrophysiological examinations of neural activity during visual processing in awake chimpanzees are currently lacking.

Methodology/principal Findings: In the present report, skin-surface event-related brain potentials (ERPs) were measured while a fully awake chimpanzee observed photographs of faces and objects in two experiments.

Brain activity in an awake chimpanzee in response to the sound of her own name.

The brain activity of a fully awake chimpanzee being presented with her name was investigated. Event-related potentials (ERPs) were measured for each of the following auditory stimuli: the vocal sound of the subject's own name (SON), the vocal sound of a familiar name of another group member, the vocal sound of an unfamiliar name and a non-vocal sound. Some differences in ERP waveforms were detected between kinds of stimuli at latencies at which P3 and Nc components are typically observed in humans.

Auditory ERPs to stimulus deviance in an awake chimpanzee (Pan troglodytes): towards hominid cognitive neurosciences.

Background: For decades, the chimpanzee, phylogenetically closest to humans, has been analyzed intensively in comparative cognitive studies. Other than the accumulation of behavioral data, the neural basis for cognitive processing in the chimpanzee remains to be clarified. To increase our knowledge on the evolutionary and neural basis of human cognition, comparative neurophysiological studies exploring endogenous neural activities in the awake state are needed.

Response to novel food in infant chimpanzees. Do infants refer to mothers before ingesting food on their own?

We investigated infant response toward novel food in captive chimpanzees under the condition in which they can explore such items freely together with their mother. Infants first approached novel foods rather than familiar ones when presented simultaneously. However, they did not ingest novel food immediately, but always sniff-licked it first.

Facial responses to four basic tastes in newborn rhesus macaques (Macaca mulatta) and chimpanzees (Pan troglodytes).

Newborn humans are known to show specific facial expressions in response to various kinds of taste stimuli and are presumed to be able to discriminate those kinds of tastes from just after birth. As the closest relatives to humans, the taste reactivity (threshold, preference and taste-elicited facial expression) of non-human primates has long been of great interest. To date, however, there have been few investigations in newborn non-human primates.

Food transfer between chimpanzee mothers and their infants.

Food sharing among chimpanzees is known to occur particularly between mothers and infants and has been proposed to be a form of parental investment. To explore the function of food sharing, it is essential to know how and what is transferred to an infant from its mother. We investigated details of interactions leading to food transfer and characteristics of items transferred in three mother-infant ( < 2 years old) pairs in captivity.