Effect of fascial Manipulation® on reaction time.

INTRODUCTION: This study aimed to investigate the effects of fascial manipulation (FM) on muscle force and electrical activity. METHODS: Sixty healthy adult participants were randomly assigned to the FM intervention group (FM group; n = 20), static stretching intervention group (SS group; n = 20), and control group (C group; n = 20). The FM group underwent FM for the right brachial fascia (antecubitus) for 210 s. The SS group underwent static stretching of the right biceps brachii for 210 s. The C group was supine for 210 s. Participants were asked to flex the right elbow joint as quickly as possible after a light signal appeared during three sessions (before, immediately after, and 1 week after the intervention). During each session, the muscle activity of the right biceps brachii and bending force of the right elbow joint were measured. We calculated the reaction time (RT), pre-motor time (PMT), motor time (MT), time to peak force (TPF), and time to peak activity (TPA) from these measurements. RESULTS: The RT, MT, TPA, and TPF of the FM group were significantly shorter immediately after or 1 week after the intervention compared with those before the intervention. The RT, MT, TPA, and TPF of the FM group were significantly shorter than those of the SS group or C group immediately after or 1 week after the intervention. CONCLUSION: FM improved RT, MT, TPA, and TPA, and the effects lasted for 1 week. Both mechanical and neurological factors may contribute to improvements in motor performance after FM.

Color Perception in Protanomalous Female Macaca fascicularis.

Protanomalous females with X chromosome-linked color vision deficiency exhibit mild abnormalities, whereas dichromats show a distinct deficiency in discriminating certain color pairs. Dichromats have an advantage in detecting a textured target when it is camouflaged by red-green colors, owing to their insensitivity to these colors. However, it is not certain whether protanomalous females possess a similar advantage in breaking camouflage. Here, we introduce an animal model of dichromatic macaque monkeys and protanomalous females. We examined whether protanomalous females have the same advantage in breaking color camouflage as shown by dichromatic macaques. We also tested whether they could discriminate a certain color pair that trichromats could, where the dichromats are confused. Our experiments show that protanomalous macaques can break color camouflage, similar to dichromats, and can discriminate colors similarly to trichromats. Protanomalous females are thus thought to have the combined ecological advantages of being both trichromats and dichromats.

Neuronal correlates of motion-defined shape perception in primate dorsal and ventral streams.

Human and non-human primates can readily perceive the shape of objects using visual motion. Classically, shape, and motion are considered to be separately processed via ventral and dorsal cortical pathways, respectively. However, many lines of anatomical and physiological evidence have indicated that these two pathways are likely to be interconnected at some stage. For motion-defined shape perception, these two pathways should interact with each other because the ventral pathway must utilize motion, which the dorsal pathway processes, to extract shape signal. However, it is unknown how interactions between cortical pathways are involved in neural mechanisms underlying motion-defined shape perception. We review evidence from psychophysical, lesion, neuroimaging and physiological research on motion-defined shape perception and then discuss the effects of behavioral demands on neural activity in ventral and dorsal cortical areas. Further, we discuss functions of two candidate sets of levels: early and higher-order cortical areas. The extrastriate area V4 and middle temporal (MT) area, which are reciprocally connected, at the early level are plausible areas for extracting the shape and/or constituent parts of shape from motion cues because neural dynamics are different from those during luminance-defined shape perception. On the other hand, among other higher-order visual areas, the anterior superior temporal sulcus likely contributes to the processing of cue-invariant shape recognition rather than cue-dependent shape processing. We suggest that sharing information about motion and shape between the early visual areas in the dorsal and ventral pathways is dependent on visual cues and behavioral requirements, indicating the interplay between the pathways.

Temporal property of single-cell activity in response to motion-defined shapes in monkey dorsal and ventral cortical areas.

In the primate brain, shape and motion are considered to be separately processed in the ventral and dorsal visual cortical areas, respectively. However, to achieve shape perception with a motion cue, shape and motion cannot be processed exclusively in separate cortical areas. Interactions between ventral and dorsal cortical areas are required, and yet, the neural mechanisms underlying motion-defined shape perception remain unclear. Here, we assessed the temporal properties of single-unit activity recorded from V4, the middle temporal area, and the anterior superior temporal sulcus while monkeys discriminated shapes defined by motion and luminance cues. Visual response latencies of V4 neurons were shorter in the luminance-cue condition than in the motion-cue condition. Meanwhile, the timings of initiation of shape selectivity were not different between cue conditions, indicating a difference in processing time. Middle temporal neurons were less shape modulated in the luminance-cue condition than in the motion-cue condition. Temporal properties of neural activities in the lower bank of anterior superior temporal sulcus were similar between cue conditions. These results suggest that an interaction of the ventral cortex with the dorsal cortex is required for shape discrimination with different visual cues.

Developmental trajectory of the corpus callosum from infancy to the juvenile stage: Comparative MRI between chimpanzees and humans.

How brains develop during early life is one of the most important topics in neuroscience because it underpins the neuronal functions that mature during this period. A comparison of the neurodevelopmental patterns among humans and nonhuman primates is essential to infer evolutional changes in neuroanatomy that account for higher-order brain functions, especially those specific to humans. The corpus callosum (CC) is the major white matter bundle that connects the cerebral hemispheres, and therefore, relates to a wide variety of neuronal functions. In humans, the CC area rapidly expands during infancy, followed by relatively slow changes. In chimpanzees, based on a cross-sectional study, slow changes in the CC area during the juvenile stage and later have also been reported. However, little is known about the developmental changes during infancy. A longitudinal study is also required to validate the previous cross-sectional observations about the chimpanzee CC. The present longitudinal study of magnetic resonance imaging scans demonstrates that the CC development in chimpanzees and humans is characterized by a rapid increase during infancy, followed by gradual increase during the juvenile stage. Several differences between the two species were also identified. First, there was a tendency toward a greater increase in the CC areas during infancy in humans. Second, there was a tendency toward a greater increase in the rostrum during the juvenile stage in chimpanzees. The rostral body is known to carry fibers between the bilateral prefrontal and premotor cortices, and is involved in behavior planning and control, verbal working memory, and number conception. The rostrum is known to carry fibers between the prefrontal cortices, and is involved in attention control. The interspecies differences in the developmental trajectories of the rostral body and the rostrum might be related to evolutional changes in the brain systems.

Elucidation of developmental patterns of marmoset corpus callosum through a comparative MRI in marmosets, chimpanzees, and humans.

The corpus callosum (CC) is present in all primate brains and is the major white matter tract connecting the cerebral hemispheres for integration of sensory, motor and higher-order cognitive information. The midsagittal area of the CC has frequently been used as a sensitive biomarker of brain development. Although the marmoset has been considered as an alternative non-human primate model for neuroscience research, the developmental patterns of the CC have not been explored. The present longitudinal study of magnetic resonance imaging demonstrated that marmosets show a rapid increase of CC during infancy, followed by a slow increase during the juvenile stage, as observed in chimpanzees and humans. Marmosets also show a tendency toward a greater increase in CC during late infancy and the juvenile stage, as observed in humans, but not in chimpanzees. However, several differences between marmosets and humans were identified. There was a tendency toward a greater maturation of the human CC during early infancy. Furthermore, there was a tendency toward a greater increase during late infancy and the juvenile stage in marmosets, compared to that observed in chimpanzees and humans. These differences in the developmental trajectories of the CC may be related to evolutional changes in social behavior.

Responses of monkey prefrontal neurons during the execution of transverse patterning.

Recent functional imaging studies have suggested that the prefrontal cortex (PF) is engaged in the performance of transverse patterning (TP), which consists of 3 conflicting discriminations (A+/B-, B+/C-, C+/A-). However, the roles of PF in TP are still unclear. To address this issue, we examined the neuronal responses in 3 regions [the principal sulcus (PS), dorsal convexity (DC), and medial prefrontal cortex (MPF)] of the macaque PF during the performance of an oculomotor version of TP. A delayed matching-to-sample (DMS) task was used as a control task. The TP task-responsive neurons were most abundant in MPF. We analyzed the dependency of each neuronal response on the task type (TP or DMS), target shape (A, B, or C), and target location (left or right). Immediately after the choice cue presentation, many MPF neurons showed task dependency. Interestingly, some of them already exhibited differential activity between the 2 tasks before the choice cue presentation. Immediately before the saccade, the number of target location-dependent neurons increased in MPF and PS. Among them, many MPF neurons were also influenced by the task type, whereas PS neurons tended to show location dependency without task dependency. These results suggest that MPF and PS are involved in the execution of TP: MPF appears to be more important in the target selection based on the TP rule, whereas PS is apparently more related to the response preparation. In addition, some neurons showed a postsaccadic response, which may be related to the feedback mechanism.

Intracranial arachnoid cysts in a chimpanzee (Pan troglodytes).

An intracranial arachnoid cyst was detected in a 32-year-old, 44.6-kg, female chimpanzee at the Primate Research Institute, Kyoto University. Magnetic resonance imaging (MRI) and computed tomography (CT) were performed and the cognitive studies in which she participated were reviewed. MRI revealed that the cyst was present in the chimpanzee's right occipital convexity, and was located in close proximity to the posterior horn of the right lateral ventricle without ventriculomegaly. CT confirmed the presence of the cyst and no apparent signs indicating previous skull fractures were found. The thickness of the mandible was asymmetrical, whereas the temporomandibular joints and dentition were symmetrical. She showed no abnormalities in various cognitive studies since she was 3 years old, except a different behavioural pattern during a recent study, indicating a possible visual field defect. Detailed cognitive studies, long-term observation of her physical condition and follow-up MRI will be continued.

Color vision test for dichromatic and trichromatic macaque monkeys.

Dichromacy is a color vision defect in which one of the three cone photoreceptors is absent. Individuals with dichromacy are called dichromats (or sometimes "color-blind"), and their color discrimination performance has contributed significantly to our understanding of color vision. Macaque monkeys, which normally have trichromatic color vision that is nearly identical to humans, have been used extensively in neurophysiological studies of color vision. In the present study we employed two tests, a pseudoisochromatic color discrimination test and a monochromatic light detection test, to compare the color vision of genetically identified dichromatic macaques (Macaca fascicularis) with that of normal trichromatic macaques. In the color discrimination test, dichromats could not discriminate colors along the protanopic confusion line, though trichromats could. In the light detection test, the relative thresholds for longer wavelength light were higher in the dichromats than the trichromats, indicating dichromats to be less sensitive to longer wavelength light. Because the dichromatic macaque is very rare, the present study provides valuable new information on the color vision behavior of dichromatic macaques, which may be a useful animal model of human dichromacy. The behavioral tests used in the present study have been previously used to characterize the color behaviors of trichromatic as well as dichromatic new world monkeys. The present results show that comparative studies of color vision employing similar tests may be feasible to examine the difference in color behaviors between trichromatic and dichromatic individuals, although the genetic mechanisms of trichromacy/dichromacy is quite different between new world monkeys and macaques.

Developmental patterns of chimpanzee cerebral tissues provide important clues for understanding the remarkable enlargement of the human brain.

Developmental prolongation is thought to contribute to the remarkable brain enlargement observed in modern humans (Homo sapiens). However, the developmental trajectories of cerebral tissues have not been explored in chimpanzees (Pan troglodytes), even though they are our closest living relatives. To address this lack of information, the development of cerebral tissues was tracked in growing chimpanzees during infancy and the juvenile stage, using three-dimensional magnetic resonance imaging and compared with that of humans and rhesus macaques (Macaca mulatta). Overall, cerebral development in chimpanzees demonstrated less maturity and a more protracted course during prepuberty, as observed in humans but not in macaques. However, the rapid increase in cerebral total volume and proportional dynamic change in the cerebral tissue in humans during early infancy, when white matter volume increases dramatically, did not occur in chimpanzees. A dynamic reorganization of cerebral tissues of the brain during early infancy, driven mainly by enhancement of neuronal connectivity, is likely to have emerged in the human lineage after the split between humans and chimpanzees and to have promoted the increase in brain volume in humans. Our findings may lead to powerful insights into the ontogenetic mechanism underlying human brain enlargement.

The influence of tempo upon the rhythmic motor control in macaque monkeys.

We examined behavioral features of isochronous repetitive movements in two macaques. The monkeys were required to press a button repetitively in response to external cues. If the cue-intervals were constant (isochronous) and sub-second, the reaction time was shorter than in random-interval condition. In contrast, in the supra-second isochronous conditions, the reaction time was not different from random-interval condition. The results suggest that the monkeys can acquire isochronous rhythms if the intervals are sub-second, probably depending on the automatic timing system. However, the conscious timing system for supra-second intervals is not well developed in monkeys, unlike humans.

Gene conversion and purifying selection shape nucleotide variation in gibbon L/M opsin genes.

BACKGROUND: Routine trichromatic color vision is a characteristic feature of catarrhines (humans, apes and Old World monkeys). This is enabled by L and M opsin genes arrayed on the X chromosome and an autosomal S opsin gene. In non-human catarrhines, genetic variation affecting the color vision phenotype is reported to be absent or rare in both L and M opsin genes, despite the suggestion that gene conversion has homogenized the two genes. However, nucleotide variation of both introns and exons among catarrhines has only been examined in detail for the L opsin gene of humans and chimpanzees. In the present study, we examined the nucleotide variation of gibbon (Catarrhini, Hylobatidae) L and M opsin genes. Specifically, we focused on the 3.6~3.9-kb region that encompasses the centrally located exon 3 through exon 5, which encode the amino acid sites functional for the spectral tuning of the genes. RESULTS: Among 152 individuals representing three genera (Hylobates, Nomascus and Symphalangus), all had both L and M opsin genes and no L/M hybrid genes. Among 94 individuals subjected to the detailed DNA sequencing, the nucleotide divergence between L and M opsin genes in the exons was significantly higher than the divergence in introns in each species. The ratio of the inter-LM divergence to the intra-L/M polymorphism was significantly lower in the introns than that in synonymous sites. When we reconstructed the phylogenetic tree using the exon sequences, the L/M gene duplication was placed in the common ancestor of catarrhines, whereas when intron sequences were used, the gene duplications appeared multiple times in different species. Using the GENECONV program, we also detected that tracts of gene conversions between L and M opsin genes occurred mostly within the intron regions. CONCLUSIONS: These results indicate the historical accumulation of gene conversions between L and M opsin genes in the introns in gibbons. Our study provides further support for the homogenizing role of gene conversion between the L and M opsin genes and for the purifying selection against such homogenization in the central exons to maintain the spectral difference between L and M opsins in non-human catarrhines.

Differential prefrontal white matter development in chimpanzees and humans.

A comparison of developmental patterns of white matter (WM) within the prefrontal region between humans and nonhuman primates is key to understanding human brain evolution. WM mediates complex cognitive processes and has reciprocal connections with posterior processing regions [1, 2]. Although the developmental pattern of prefrontal WM in macaques differs markedly from that in humans [3], this has not been explored in our closest evolutionary relative, the chimpanzee. The present longitudinal study of magnetic resonance imaging scans demonstrated that the prefrontal WM volume in chimpanzees was immature and had not reached the adult value during prepuberty, as observed in humans but not in macaques. However, the rate of prefrontal WM volume increase during infancy was slower in chimpanzees than in humans. These results suggest that a less mature and more protracted elaboration of neuronal connections in the prefrontal portion of the developing brain existed in the last common ancestor of chimpanzees and humans, and that this served to enhance the impact of postnatal experiences on neuronal connectivity. Furthermore, the rapid development of the human prefrontal WM during infancy may help the development of complex social interactions, as well as the acquisition of experience-dependent knowledge and skills to shape neuronal connectivity.

Neuronal activity during discrimination of shapes defined by motion in area V4.

To investigate the neuronal mechanisms of motion-defined shape processing, we examined single-neuron activity in area V4 in monkeys performing a shape discrimination task under the shape-from-motion (SFM) condition, in which a motion cue is critical for shape perception, and under the shape-from-luminance (SFL) condition, in which a luminance cue is critical. About 35% (30 of 86) of neurons responded selectively to shapes under both the SFM and SFL conditions. These neurons showed a similar shape preference between the SFM and SFL conditions. There was a weak tendency of lower shape selectivity in error trials. These results suggest the involvement of V4 in SFM processing as well as in SFL processing.

Feature to space conversion during target selection in the dorsolateral and ventrolateral prefrontal cortex of monkeys.

To investigate the neuronal mechanism of the process of selection of a target from an array of stimuli, we analysed neuronal activity of the lateral prefrontal cortex during the response period of a serial probe reproduction task. During the response period of this task, monkeys were trained to select a memorized target object from an array of three objects and make a saccadic eye movement toward it. Of 611 neurons, 74 neurons showed visual response and 56 neurons showed presaccadic activity during the response period. Among visual neurons, 27 showed array- and target-selectivity. All of these array- and target-selective visual responses were recorded from the ventrolateral prefrontal cortex (VLPFC). Among 56 neurons with presaccadic activity, nine showed target-selective activity, 17 showed target- and direction-selective activity, and 23 showed direction-selective activity. The target-selective, and the target- and direction-selective activities were recorded from the VLPFC, and the direction-selective activities were recorded from VLPFC and dorsolateral prefrontal cortex (DLPFC). The starting time of the activity was earlier for the target-selective, and target- and direction-selective activities in VLPFC, intermediate for the direction-selective activities in VLPFC, and later for the direction-selective activities in DLPFC. These results suggest that VLPFC plays a role in the process of selection of a target object from an array of stimuli, VLPFC and DLPFC play a role in determining the location of the target in space, and DLPFC plays a role in selecting a direction and making a decision to generate a saccadic eye movement.

Classification of extracellularly recorded neurons by their discharge patterns and their correlates with intracellularly identified neuronal types in the frontal cortex of behaving monkeys.

Neurons in the cerebral cortex are not homogeneous. However, neuronal types have been ignored in most previous work studying neuronal processes in behaving monkeys. We propose a new method to identify neuronal types in extracellular recording studies of behaving monkeys. We classified neurons as either bursting or non-bursting, and then classified the bursting neurons into three types: (i) neurons displaying a burst of many spikes (maximum number of spikes within a burst; NSB max > or = 8) at a high discharge rate (maximum interspike interval; ISI max < 5 ms); (ii) neurons displaying a burst of fewer spikes (NSB max < or = 5) at a high discharge rate (ISI max < 5 ms); and (iii) neurons displaying a burst of a few spikes (NSB max < or = 7) at relatively long ISIs (ISI max > 5 ms). We found that the discharge patterns of the four groups corresponded to those of regular spiking (RS), fast spiking (FS), fast rhythmic bursting (FRB) and intrinsic bursting (IB) neurons demonstrated in intracellular recording studies using in vitro slice preparations, respectively. In addition, we examined correlations with the task events for neurons recorded in the frontal eye field and neuronal interactions for pairs of neurons recorded simultaneously from a single electrode. We found that they were substantially different between RS and FS types. These results suggest that neurons in the frontal cortex of behaving monkeys can be classified into four types based on their discharge patterns, and that these four types contribute differentially to cortical operations.

Context-dependent representation of reinforcement in monkey amygdala.

It has been reported that neurons in the amygdala respond to visual cues that predict reward and aversive outcomes. However, it remains unclear whether the representation of reinforcement in the amygdala depends on the relative preference for an outcome compared with another simultaneously available outcome. In this study, we introduced three reinforcements (juice, water, and electrical stimulus) and used two of them in one experimental block. Of 52 neurons that showed cue responses reflecting the outcome information, 23% of amygdala neurons coded preferred outcomes, whereas only one neuron coded nonpreferred outcomes. These proportions of amygdala were significantly different from those of the orbitofrontal cortex, which had both types of neurons.

Modulation of V4 shifts from dependent to independent on feature during target selection.

We analyzed neuronal activities of visual area V4 of monkeys performing a delayed visual search task. To examine the temporal profile of factors influencing the neuronal activities, we conducted multiple regression analyses at 5 ms steps. During the period from 110 to 155 ms after the stimulus onset, there were neurons whose activity was suppressed when a target was presented near but beyond the neuron's receptive field (RF) compared to that when a target was within the RF. We referred this suppressive effect as an early period modulation. During the period from 155 to 280 ms after the stimulus onset, V4 activities were suppressed when a target was presented in any location outside of the neuron's RF. We referred this suppressive effect as a late period modulation. The magnitudes of the effect were equivalent across target locations when a target was beyond its RF. At the population level, while the modulation in the early period was correlated with stimulus selectivity, the modulation in the late period did not show such a correlation. These results suggest that V4 neurons have at least two distinct phases of modulations and those modulations contribute to select a target in the visual search task.

Top-down signal of retrieved information from prefrontal to inferior temporal cortices.

We compared neuronal activities in the ventrolateral prefrontal cortex (VLPFC) and the inferior temporal cortex (IT) during the retrieval of an object from the working memory. About one third of IT neurons showed color- and target-selective (CT) or target-selective (T) response during the color cue period of the serial probe reproduction (SPR) task. These object-selective (CT and T) responses in IT could be correlated with the retrieval process of an object from the memorized multiple objects because no objects were presented during this period. However, proportion of CT and T responses was smaller in IT than in VLPFC, where two thirds of neurons showed object-selective response. In addition, object-selective response started earlier in VLPFC than in IT. These results suggest that VLPFC retrieves particular object information from the working memory and sends the retrieved object information to IT. The fact that the responses in the error trials did not decrease in IT suggests that IT is not a critical area for the retrieval process from the working memory.

Neurons in the macaque orbitofrontal cortex code relative preference of both rewarding and aversive outcomes.

Many studies have shown that the orbitofrontal cortex (OFC) is involved in the processing of emotional information. However, although some lines of study showed that the OFC is also involved in negative emotions, few electrophysiological studies have focused on the characteristics of OFC neuronal responses to aversive information at the individual neuron level. On the other hand, a previous study has shown that many OFC neurons code relative preference of available rewards. In this study, we aimed to elucidate how reward information and aversive information are coded in the OFC at the individual neuron level. To achieve this aim, we introduced the electrical stimulus (ES) as an aversive stimulus, and compared the neuronal responses to the ES-predicting stimulus with those to reward-predicting stimuli. We found that many OFC neurons showed responses to both the ES-predicting stimulus and the reward-predicting stimulus, and they code relative preference of not only the reward outcome but also the aversive outcome. This result suggests that the same group of OFC neurons code both reward and aversive information in the form of relative preference.