Ayako Ajima

Geometrical and topological relationships between multiple functional maps in cat primary visual cortex

The mammalian striate cortex is organized such that the receptive field properties of neighboring neurons change gradually across the cortical surface, forming so-called cortical maps. The presence of such maps has been demonstrated in different species of mammals for several parameters characterizing the visual space: retinotopy, ocular dominance, orientation, direction of motion and spatial frequency. In this study we used the optical imaging of intrinsic signals to simultaneously record the multiple functional maps in the same animal in order to obtain a comprehensive set of rules that govern mutual dependencies among the functional maps. Our results indicate that while orientation, direction and ocular dominance are represented on the cortex in a mutually dependent manner, the representation of spatial frequency is independent of the other types of cortical representations. The presence and/or absence of mutual dependence among the multiple functional maps are suggested to provide an important clue for the understanding of the development of visual cortical information representation in neonatal animals.

Online analysis method for intrinsic signal optical imaging

The intrinsic optical imaging technique has been widely applied for the visualization of functional maps in the sensory cortices of mammals. Many current studies refer this mapping in order to focus thereafter on particular features, at some particular locations: a fast and accurate mapping is therefore required. However, even during a successful experiment, the recorded raw data are usually contaminated by some kinds of noise that cannot necessarily be averaged out over the trials. An adequate image data analysis method has to be applied to extract signals closely related neural activities in response to presented stimuli. Thus far two different analysis methods could be adopted: the band-pass filtering and the GIF method [Yokoo T, Knight BW, Sirovich L. An optimization approach to signal extraction from noisy multivariate data. NeuroImage 2001:14;1309-26]. While the latter one is very efficient but requires the whole data in order to maximize the signal to noise ratio, the simple band-pass filtering technically reaches its limits very quickly. Here we propose another filtering method based on the polynomial subtraction of spatially smoothly modulated components. This simple method can visualize well-organized iso-orientation domains of the cat visual cortex with reliability similar to more sophisticated ones while allowing an online visualization of the clean data.

GABA-mediated representation of temporal information in rat barrel cortex.

Temporal sequences of inputs to the rat whiskers are thought to be important to recognize the environment of the rat. In this study, we applied combined stimulations to neighboring whiskers D1 and D2, and the cortical activities evoked in the rat barrel cortex were measured using the intrinsic optical imaging technique. The timing of stimulation to neighboring whiskers affected the evoked cortical activities: the cortical activity evoked by in-phase stimulation to D1 and D2 was significantly stronger than that evoked by out-of-phase stimulation. In order to elucidate the mechanism underlying this phenomenon, the effect of blockade of cortical inhibitory circuits was examined. Iontophoretic application of bicuculline or saclofen (GABA-A or GABA-B antagonist) increased the evoked cortical activities and diminished the difference in activities obtained with in-phase and anti-phase stimulation. These results suggest that local inhibitory circuits play a critical role in coding temporal information of whisker stimulation.

Coincidence of ipsilateral ocular dominance peaks with orientation pinwheel centers in cat visual cortex

Geometrical relationships among multiple cortical maps, such as those between ocular dominance and orientation maps, are a prominent feature of the brains functional architecture. It is also well known that there is a strong bias of cortical responses toward the contralateral eye during early postnatal development. We wondered therefore whether and how such an imbalance of cortical responsiveness in a developing animal might influence the mutual geometrical relationships between orientation and ocular dominance maps in adult animals. The results of our study indicate the existence of a strong tendency for the peaks of the ipsilateral eye domains to coincide with the location of point singularities (pinwheel centers) in orientation maps. No such relationship was found for the peaks of contralateral eye domains. Computational studies reproduced similar asymmetry in the coincidence under the contralateral eye bias of inputs. Our study raised the idea that the pinwheel centers play an important role for retaining the weaker ipsilateral eye inputs during normal development.

The Claustrum Coordinates Cortical Slow-Wave Activity

During sleep and awake rest, the neocortex generates large-scale slow-wave activity. Here we report that the claustrum, a poorly understood subcortical neural structure, coordinates neocortical slow-wave generation. We established a transgenic mouse line allowing genetic and electrophysiological interrogation of a subpopulation of claustral glutamatergic neurons. These claustral excitatory neurons received inputs from glutamatergic neurons in a large neocortical network. Optogenetic activation of claustral neurons in vitro induced excitatory post-synaptic responses in most neocortical neurons, but elicited action potentials primarily in inhibitory interneurons. Optogenetic activation of claustral neurons in vivo induced a Down-state featuring a prolonged silencing of neural acticity in all layers of many cortical areas, followed by a globally synchronized Down-to-Up state transition. These results demonstrate a crucial role of the claustrum in synchronizing inhibitory interneurons across the neocortex for spatiotemporal coordination of brain state. Thus, the claustrum is a major subcortical hub for the synchronization of neocortical slow-wave activity.

RA pacemaker-like spontaneous firing modulated song productions in zebra finch

s / Neuroscience Research 71S (2011) e108–e415 e283 posterior cingulate activity was significantly higher during proximity to the unfamiliar other than during isolation. The posterior cingulate activity during proximity to the unfamiliar other was marginally correlated with offensive social response during the direct encounter. The present findings suggest that the disparate domains of MCS may be involved in impression and expression of social response in marmosets as similar to human studies, a part of which may be under serotonergic regulation. Research fund: KAKENHI (19591388). doi:10.1016/j.neures.2011.07.1234 P3-p10 Characterization of escalated aggression by GABAB receptor activation in the dorsal raphe nucleus Aki Takahashi 1 , Klaus A. Miczek 2, Tsuyoshi Koide 1 1 Mouse Genomics Resource Laboratory, National Institute of Genetics (NIG), Mishima, Japan 2 Tufts University, Medford, MA, USA Violence and escalated forms of aggressive behavior are major issues in public health; violence kills more than 1.6 million people every year worldwide. The serotonin (5-HT) system in the brain has been implicated in the neurobiological mechanisms of escalated aggression. The 5-HT neurons in the mammalian forebrain originate mainly from a midbrain structure, the dorsal raphe nucleus (DRN). Previously, we have shown that pharmacological activation of GABAB receptors in the DRN increased 5-HT release in the medial prefrontal cortex, and also increased aggressive behavior in male mice. In this study, we characterized this escalated aggression in more detail in order to learn whether this aggressive behavior can be affected by (1) previous fighting experiences, (2) the location of the aggressive confrontation, or (3) time of day. Detailed behavioral analysis showed that the intra-DRN administration of GABAB receptor agonist baclofen enhanced aggressive behaviors even in animals without fighting experience, and also in unfamiliar surroundings where aggressive behavior is usually inhibited. This escalated aggression induced by baclofen may be characterized as “abnormal” aggression because the animals attacked vulnerable body targets of intruders that are typically not the targets of attack. However, these resident males did not attack females. Thus, intra-DRN baclofen specifically escalates inter-male aggression in a species-atypical manner. We also found that intra-DRN baclofen preferentially escalated aggression during the dark-period of day (20:0024:00), but not during the light-period (12:00-15:30). This may be due to distinct modulation of DRN 5-HT neurons by GABAB receptors at different times of day. To understand the neural pathway involved in the DRN-GABAB heightened aggression, we are currently examining cFos expression in several forebrain areas. Research fund: KAKENHI (23683021). doi:10.1016/j.neures.2011.07.1235 P3-p11 Different temporal pattern of information processing about facial emotion conveyed by single neurons between the monkey amygdala and ventrolateral prefrontal cortex Koji Kuraoka , Katsuki Nakamura Sec. of Cog. Neurosci., Primate Res. Inst., Kyoto Univ., Inuyama, Japan Face can convey a variety of social information. The recognition of facial emotion and/or identity has been well studied. In the monkey brain, face responsive neurons have been recorded from several areas, such as the inferior temporal cortex (IT), the superior temporal sulcus (STS), the amygdala, and the ventrolateral prefrontal cortex (VLPFC). Among these areas, the amygdala and VLPFC are implicated in the related to social and emotional behavior. However, the details of the processing of facial emotion or identity and the functional differences between these two areas remain unclear. Thus, in this study, we recorded the activity of single neurons from the amygdala and VLPFC while presenting several video clips of three types of facial emotion recorded from three model monkeys. We calculated the amount of information about facial emotion and identity conveyed by neuronal populations in the amygdala and VLPFC. 76 out of 187 (41%) neurons in the amygdala and 53 of 102 (52%) neurons in the VLPFC responded to the video stimuli. The amount of information about identity conveyed by the VLPFC neurons as well as the amygdala neurons became high immediately after the stimulus presentation. By contrast, the amount of information about facial emotion conveyed by the amygdala neurons sharply increased just after the stimulus presentation whereas that conveyed by the VLPFC neurons increased gradually after stimulus presentation. These results indicate that the monkey VLPFC processes information about facial emotion slower than the amygdala. The amygdala probably uses the emotional information to generate acute emotional behavior while the VLPFC probably uses the information to plan more complex and social behavior. The different temporal pattern of emotional information processing may reflect these functional differences. Research fund: KAKENHI (21120009). doi:10.1016/j.neures.2011.07.1236 P3-p12 RA pacemaker-like spontaneous firing modulated song productions in zebra finch Ayako Ajima 1 , Raimu Imai 2, Chihiro Mori 2, Kazuhiro Wada 2, Neal A. Hessler 1 1 Lab. for Vocal Behavior Mechanisms, BSI, RIKEN 2 Div. Integrated Life Science, Faculty of Advanced Life Science, Hokkaido Univ Birdsong, like human speech, requires precise control of vocal and respiratory muscles. In a key nucleus of muscle-control, the robust nucleus of arcopallium (RA), neurons display a tonic, pacemaker-like activity at rest, while activity becomes highly phasic with prolonged silent periods during singing. The aim of this study was to elucidate the function of RA pacemakerlike spontaneous firing on adult song production. We first used brain slices containing RA nucleus to examine electrophysiological properties and found that tonic activity of RA neurons was independent from synaptic inputs. RA neuron contained Ih potassium current, and its pharmacological block reduced the frequency of tonic firing. To examine the effect of tonic activity on singing in vivo, we injected Ih current blocker though implanted cannulae and observed song production and behavior. Block of the Ih current reduced the frequency of singing, but did not alter song structure. We conclude that the frequency of tonic activity of RA neurons is a regulator controlling song production. Neuromodulatory system such as catecholamines may affect the tonic activity, which could control the behavioral state, and level of motivation. To clarify the influences of catecholamines on RA neuron activity and/or singing, we currently measure dopamine/noradrenaline levels in RA by in vivo voltammetry method. doi:10.1016/j.neures.2011.07.1237 P3-p13 Relationship between task performance and prefrontal cortex activity during working memory tasks: An optical topography study Ryuta Aoki 1,2 , Hiroki Sato 3, Takusige Katura 3, Ryoichi Matsuda 1, Hideaki Koizumi 3 1 Grad. Sch. of Arts and Sci., Univ. of Tokyo, Tokyo 2 JSPS Res. Fellow 3 Hitachi, Ltd., Central Res. Lab., Saitama Introduction: Prefrontal cortex (PFC) activity during cognitive tasks is known to reflect individual differences in task performance. However, whether better task performance (higher accuracy and faster response speed) is related to greater or lesser PFC activity remains unclear. We investigated the relationship between task performance and PFC activity during spatial and verbal working memory (WM) tasks by using optical topography (OT), a non-invasive neuroimaging technique based on near-infrared spectroscopy (NIRS). Measurements: Ninety healthy adults (45 women; mean age = 33.5 years) performed spatial and verbal WM tasks that had an identical delayed-response paradigm. PFC activity was measured using a 52-channel OT system. Analysis: Increases in the oxy-hemoglobin (oxy-Hb) signal over the baseline values during the WM tasks were used as an index of PFC activation. The magnitude of PFC activation for each channel, task condition, and participant was expressed using z-values (converted from t-statistics) taking inter-trial variability into consideration. Correlations between PFC activity (increases in the oxy-Hb signal) and individual performance measures (accuracy and reaction time) were separately assessed for each task condition. Results: We observed significant PFC activation during the WM tasks, especially in the dorsolateral PFC (DLPFC) on both hemispheres. For both WM tasks, PFC activity was positively correlated with accuracy of performance and negatively correlated with reaction time. In particular, the right DLPFC activity during the spatial WM task showed a significant negative correlation with accuracy. Conclusion: We showed that PFC activity during the WM tasks, which was measured using OT, is associated with increased task performance. Our results suggest that OT signals recorded from the PFC reflect higher levels of concentration on ongoing tasks or readiness for upcoming tasks, which leads to better task performance. doi:10.1016/j.neures.2011.07.1238

Differential activities in rat barrel cortex evoked by combined stimulation to neighboring whiskers with various time delays: an optical imaging study

Barrels in the rodent vibrissa cortex play a key role in signal processing of whisker sensitivity. To compare responses between neurons within the barrels and those outside, rat neocortical unit responses to ramp-and-hold whisker deflections with six different onset velocities (100-2.5 mm/s) and four different plateau amplitudes (2-0.2 mm) were recorded. Twenty-four (6 X 4) peristimulus-time histograms were construted. The amplitude dependence of responses was evaluated by calculating F values of analysis of variance to test the degree of overall difference among plateau responses of 4 amplitudes, and similarly the velocity dependence by F value based on 6 sets of transient responses. Of 61 neurons studied, 32 were barrel neurons, 29 being non-barrel neurons. The amplitude dependence was greater for the former than for the latter (mean F value: 5.27 vs 2.13). Conversely, the velocity dependence was smaller for the barrel neurons than for the non-barrel neurons (F: 2.76 vs 3.20).