Encoding of stimulus identity, memory, and reward expectation in monkey perirhinal cortex during delayed conditioning

Abstracts synaptic weights to develop in time according to the states of the pre- and postsynaptic neurons. We consider the situation that the nature of synaptic plasticity can be characterized by a few parameters. As a result, we can systematically investigate the emergent behaviors of our model, and we found that the network exhibits three typical behaviors, depending on the nature of the synaptic plasticity. doi:10.1016/j.neures.2009.09.1334

P3-i19 Firing dynamics of the inferior olive neurons: a simulation study Miho Onizuka 1,2 , Nicolas Schweighofer 3 , Yuichi Katori 4,5 , Kazuyuki Aihara 4,5 , Hideaki Ogasawara 1,6 , Keisuke Toyama 1 , Mitsuo Kawato 1,2 1

ATR CNS, Kyoto, Japan; 2 Grad. Sch. Inf. Sci., NAIST, Nara, Japan; USA; 4 ERATO, JST, Tokyo, Japan; 5 IIS, Univ. Tokyo, Tokyo, Japan; Kyoto, Japan

3 6

USC, NiCT,

Dendrites of the inferior olive (IO) neurons form glomeruli where their dendritic spines are interconnected through gap junctions and receive cerebellar nuclear inhibition. When the inhibition is blocked by local administration of picrotoxin (PIX) to IO, firing of IO cells starts to alternate between the rhythmic-synchronized burst and desynchronized-sporadic firing states. A previous simulation study assuming increased gap junction conductance in the PIX than normal condition reproduced this firing pattern. However, this assumption is inaccurate, since PIX reduces the inhibition rather than increases the gap junction conductance. We improved the model so as to reproduce the reduced inhibitory conductance and reproduced firing dynamics of IO neurons in normal and PIX conditions, and further estimated the gap junction and inhibitory conductances in the two conditions as those give the best fit the experimental results. doi:10.1016/j.neures.2009.09.1335

P3-i20 Simultaneous adaptation to opposing force fields with different motor plans Masaya Hirashima, Daichi Nozaki The University of Tokyo, Japan Human subjects can adapt to novel perturbations by changing their internal model of the environment. However, it is not understood whether perturbations are represented with respect to the actual or planned movement. To test between these two hypotheses we used a novel adaptation paradigm. The target was alternately presented either at 30◦ clockwise (CW) or at counter-clockwise (CCW) position from straight ahead whereas a cursor was rotated by 30◦ CW for the CW target and 30◦ CCW for the CCW target. Thus, the two different movement plans (CW or CCW target) needs to result in the identical hand movement to the straight forward direction. After subjects adapted to this visuomotor rotation task, they were further exposed to two opposing curl force fields; the CW and CCW fields were applied for the CW and CCW targets, respectively. Significant improvement of performance and after-effects in catch trials were observed. This suggests that internal models are acquired with respect to the planned movement and that the redundant neural networks in the brain can differently accomplish an identical actual movement. doi:10.1016/j.neures.2009.09.1336

P3-j01 The nucleus locus coeruleus/subcoeruleus inhibits the defensive-like, immobile posture following air-puff startle in the rat Junichiro Tamaki, Masayoshi Tsuruoka, Masako Maeda, Bunsho Hayashi, Tomio Inoue Dept. Physiol., Showa Univ., Tokyo, Japan Following the air-puff startle, rats assume a defensive-like, immobile posture (DIP) of approximately 2–3 s in length. The DIP period is considered as an attentional state or vigilance condition in which rats judge their circumstance. The present study was to examine the effect of bilateral lesions of the locus coeruleus/subcoeruleus (LC/SC) on the DIP. Two weeks before experiments, bilateral lesions of the LC/SC were made by neurotoxin 6-OHDA (6 ␮g). The startle amplitude (SA) and the DIP period were measured with a modified stabilimeter. In the LC/SC-lesioned rats (n = 8), when an air-puff stimulus (14.4 psi in strength, 100 ms in duration) was applied, the DIP period was significantly reduced by 83% of the value before lesions, as well as in the decrease of the SA (59% of the value before lesions). In the control sham-operated rats (n = 6), both the SA and the DIP period did not produce any change. These results suggest that the LC/SC is involved in the DIP in which rats judge their circumstance in the air-puff startle condition. doi:10.1016/j.neures.2009.09.1337

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P3-j02 Encoding of stimulus identity, memory, and reward expectation in monkey perirhinal cortex during delayed conditioning Kaoru Uchiyama 1,2 , Narihisa Matsumoto 2 , Munetaka Shidara 1,2 , Yasuko Sugase-Miyamoto 2 1

Univ. of Tsukuba, Tsukuba, Japan;

2

AIST, Tsukuba, Japan

To investigate neuronal processing in perirhinal cortex during stimulus-stimulusreward associations, we recorded single unit data from 103 neurons in areas 35/36 using two monkeys performing bar-release response trials imbedded within a delayed conditioning paradigm. In each trial, a color cue and a pattern cue were presented sequentially. Each pattern cue was associated with either rewarded or unrewarded outcomes depending on the preceding color cue. The monkeys reacted more quickly in rewarded trials than in unrewarded trials, showing that they had learned the contingencies between the reward and the color-pattern cue sequences. The pattern cues elicited selective responses from 58/103 (56%) neurons. 47/103 (81%) were selective for the pattern, 18/103 (31%) for the preceding color, and 20/103 (34%) for the reward contingency. The result shows that the perirhinal neurons have signals about stimulus identity, memory for a preceding stimulus, and predicted reward contingency, suggesting a role in associating these three types of signals. doi:10.1016/j.neures.2009.09.1338

P3-j03 Response properties of neurons in the monkey parahippocampal cortex during the navigation through a virtual environment Shumpei Unno 1 , Nobuya Sato 2 , Masato Taira 1 1

ARISH, Nihon Univ., Tokyo, Japan; Gakuin Univ., Nishinomiya, Japan

2

Dept. Integrated Psychol. Sci., Kwansei

To investigate the neuronal mechanisms underlying navigation, neurons were recorded in the parahippocampal cortex (PHC) and the medial parietal region (MPR) while the monkey actively navigated through the virtual environment. A trial was begun by the presentation of a destination room (the cue period). Then the monkey was required to move from the starting point to the destination room by operating the joystick. A majority of responsive neurons in the PHC (12/13) responded during the cue period. Many of them showed a significant preference for a particular room during the cue period. The occurrence rate of cue-responsive neurons in the PHC was significantly higher than that in the MPR (14/30, ␹2 (1) = 7.90, p < 0.01). These results might indicate a possible difference in roles in navigation between the PHC and the MPR. doi:10.1016/j.neures.2009.09.1339

P3-j04 Difference of neural activities modulated by top-down attention in face and object processing: An MEG study Tomoaki Ayabe 1,2 , Kensaku Miki 1,2 , Tomohiro Ihizu 2,3 , Kaoru Amemiya 2,4 , Ryusuke Kakigi 1,2 1

National Institute for Physiological Sciences, Okazaki, Japan; 2 Graduate University for Advanced Studies, Hayama, Japan; 3 Graduate School of 4 Graduate School of Human Relation, Keio University, Tokyo, Japan; Medicine, University of Tokyo, Tokyo, Japan Although top-down attention can modulate early neural activities in extrastriate cortices for object processing, no consensus has yet been reached time course of early modulation for face and other object processing. To address this issue, we adopted a double-exposure visual stimulus superimposed of face and house images and asked subjects to attend either one. Measuring magnetoencephalogram (MEG), we found top-down attention can enhance neural activities in right occipito-temporal area and right STS activities for face processing in 170 and 230 ms, respectively. For house processing, on the contrary, an only STS activity in 230 ms was modulated. These results suggested that top-down attention have a different effect between face and other object processing, which top-down attention can have a preferred and early access to face processing. doi:10.1016/j.neures.2009.09.1340

P3-j05 The attentional modulation to subliminaol and supraliminal processing of word Atsushi Matsumoto, Norihiro Sadato National Institute for Physiological Sciences, Japan In order to investigate the neural basis of attentional modulation to subliminal processing, we manipulated the attention to subliminally presented word by using auditory warning signal preceding to a target stimuli and the brain activation was