Masumi Wakita

Broca's area processes the hierarchical organization of observed action.

Brocas area has been suggested as the area responsible for the domain-general hierarchical processing of language and music. Although meaningful action shares a common hierarchical structure with language and music, the role of Brocas area in this domain remains controversial. To address the involvement of Brocas area in the processing action hierarchy, the activation of Brocas area was measured using near-infrared spectroscopy. Measurements were taken while participants watched silent movies that featured hand movements playing familiar and unfamiliar melodies. The unfamiliar melodies were reversed versions of the familiar melodies. Additionally, to investigate the effect of a motor experience on the activation of Brocas area, the participants were divided into well-trained and less-trained groups. The results showed that Brocas area in the well-trained participants demonstrated a significantly larger activation in response to the hand motion when an unfamiliar melody was played than when a familiar melody was played. However, Brocas area in the less-trained participants did not show a contrast between conditions despite identical abilities of the two participant groups to identify the melodies by watching key pressing actions. These results are consistent with previous findings that Brocas area exhibits increased activation in response to grammatically violated sentences and musically deviated chord progressions as well as the finding that this region does not represent the processing of grammatical structure in less-proficient foreign language speakers. Thus, the current study suggests that Brocas area represents action hierarchy and that sufficiently long motor training is necessary for it to become sensitive to motor syntax. Therefore, the notion that hierarchical processing in Brocas area is a common function shared between language and music may help to explain the role of Brocas area in action perception.

Measurement of neuronal activity in a macaque monkey in response to animate images using near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) has been used extensively for functional neuroimaging over the past decade, in part because it is considered a powerful tool for investigating brain function in human infants and young children, for whom other neuroimaging techniques are not suitable. In particular, several studies have measured hemodynamic responses in the occipital region in infants upon exposure to visual stimuli. In the present study, we used a multi-channel NIRS to measure neuronal activity in a macaque monkey who was trained to watch videos showing various circus animals performing acrobatic activities without fixing the head position of the monkey. Cortical activity from the occipital region was measured first by placing a probe comprising a 3 × 5 array of emitters and detectors (2 × 4 cm) on the area (area 17), and the robustness and stability of the results were confirmed across sessions. Cortical responses were then measured from the dorsofrontal region. The oxygenated hemoglobin signals increased in area 9 and decreased in area 8b in response to viewing the videos. The results suggest that these regions are involved in cognitive processing of visually presented stimuli. The monkey showed positive responsiveness to the stimuli from the affective standpoint, but its attentional response to them was an inhibitory one.

Interaction between Perceived Action and Music Sequences in the Left Prefrontal Area

Observing another persons piano play and listening to a melody interact with the observers execution of piano play. This interaction is thought to occur because the execution of musical-action and the perception of both musical-action and musical-sound share a common representation in which the frontoparietal network is involved. However, it is unclear whether the perceptions of observed piano play and listened musical sound use a common neural resource. The present study used near-infrared spectroscopy to determine whether the interaction between the perception of musical-action and musical-sound sequences appear in the left prefrontal area. Measurements were obtained while participants watched videos that featured hands playing familiar melodies on a piano keyboard. Hand movements were paired with either a congruent or an incongruent melody. Two groups of participants (nine well-trained and nine less-trained) were instructed to identify the melody according to hand movements and to ignore the accompanying auditory track. Increased cortical activation was detected in the well-trained participants when hand movements were paired with incongruent melodies. Therefore, an interference effect was detected regarding the processing of action and sound sequences, indicating that musical-action sequences may be perceived with a representation that is also used for the perception of musical-sound sequences. However, in less-trained participants, such a contrast was not detected between conditions despite both groups featuring comparable key-touch reading abilities. Therefore, the current results imply that the left prefrontal area is involved in translating temporally structured sequences between domains. Additionally, expertise may be a crucial factor underlying this translation.

Discrimination training of auditory patterns in a common marmoset

localization of such specialized neuronal networks has not been investigated. Furthermore, most of these neurons have been classified from the signatures they leave in multiunit activity (MUA), but the relationships that neuronal spiking holds with the underlying sub/supra-threshold postsynaptic activities have not been clarified yet. We used extracellular potentials recorded simultaneously from 64 sites inside the A1 of adult Wistar rats to evaluate neuronal codifiers for fundamental attributes, which were selected from their particular MUA dose-response curves. We demonstrated that the underlying neuronal populations were sparsely and heterogeneously distributed along the A1, even though they complied with the tonotopic organization. Codifying neurons were majorly PCs which showed laminar profiles. MUA was correlated to Beta (12–25 Hz) postsynaptic oscillations in the infragranular layers, while the supragranular layers revealed a better correlation between MUA and Gamma range postsynaptic oscillations (70–170 Hz). We concluded that, for rats, sounds are codified in A1 by a sparsely segregated network involving specialized PCs and that their postsynaptic activity may create the proper conditions for the emergence of sparse and dense spiking patterns.

Intrinsic signal recording from a monkey whose behavior was maintained by a schedule of reinforcement

Optical recording of cortical activity in awake monkeys has enhanced our understanding of the functional anatomy of the primary visual cortex (V1). However, cortical representation of visual cognition has not been studied by optical recording, even though the greatest merit of using awake animals is that they can offer advantages in studying cognitive function that anesthetized animals cannot. Thus far, the optical recording method has not been combined with tasks that accompany body movements because of concern about movement noise, although behavioral tasks are helpful in the study of animal cognition. Here, I tested the influence of body movements during the signal acquisition period on the resultant images. I recorded the intrinsic signals associating with different orientations from V1 of a monkey who was emitting behavior during the signal acquisition period. Although the monkeys behavior was maintained on a variable-interval schedule that typically induces a high rate of response, orientation maps were consistently obtained. Therefore, a successful recording under this operant regimen implies the applicability of the optical recording method to other behavioral tasks. Several constraints in applying optical recording to studies using behaving animals are also discussed.

Changes in binocular responses of visual cortical neurons induced by tetanic stimulation of the optic nerve in free-moving kittens

Binocular responsiveness of most neurons in the primary visual cortex of cats can be changed by monocular visual deprivation during the critical period of early postnatal life. These results suggest that impulse activity from both optic nerves is important for the formation of ocular dominance of cortical neurons. A form of synaptic plasticity, long-term potentiation (LTP), has been hypothesized to be involved in such an experience-dependent change in the cortex. However, there has been no direct experimental demonstration of the hypothesized link between LTP and ocular dominance plasticity of cortical neurons. In kittens at postnatal 23-47days, we activated one of the optic nerves with tetanic stimulation of the 0 -burst type (4 trains at 100 Hz given at 5 Hz for 2 s at an interval of 10 s for 48 hours) which is known to induce LTP in the visual cortex and analyzed possible changes in visual response of neurons in the lateral geniculate nucleus (LGN) and the visual cortex. After this tetanic stimulation, most of the cortical neurons (n = 224) had normal orientation selectivity to moving light bar stimulus from both eyes. Also, most LGN neurons had normal responses to visual stimuli. On the other hand, the ocular dominance of most cortical neurons shifted toward the eye at the tetanized side in all the animals (n = 7). These results indicate that chronic electrical stimulation of the LTP-inducing type changes the ocular dominance of cortical neurons.

1306 Critical period for sparing of function after neonatal lesion of the auditory cortex in rats

Masumi Wakita It has been previously reported that bilateral damage in the auditory cortex resulted in a severe deficit in the acquisition of the auditory pattern discrimination if it was incurred at adulthood while animals with comparative lesion on the day of birth could learn the discrimination. In the present report, a critical period for sparing of auditory pattern discrimination was surveyed behaviorally in rats sustaining neonatal lesion in the auditory cortex. Consequently, rats with such lesions before weaning could learn the tasks as intact animals. On the contrary, rats who sustained comparative lesions after weaning could not learn this discrimination. These findings imply that auditory pattern discrimination was spared from early brain damage if the brain is injured before cortical function and circuitry are under development.