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Primate prefrontal activities reflects competition among multiple directionally defined choices
S192
Abstracts
P2-o03 Neuronal representation of visual saliency in the macaque posterior parietal cortex Tomohiro Tanaka, Atsushi Fujimoto, Tadashi Ogawa Graduate School of Medicine, Kyoto University, Kyoto, Japan A salient stimulus (a red target among green distractors) can automatically attract our attention. To examine neural representation of visual saliency, we trained monkeys to perform a visual search task in which a singleton target was different from distractors in color. We manipulated the degree of visual saliency of the target by independently changing “target-distractor color contrast” and “stimulusbackground luminance contrast”. For the estimation of the degree of visual saliency, we used saccade latency. Both contrasts can modulate saccade latency (when one of the contrasts larger, saccade latency became shorter). We found that these two contrasts differentially modulated neuronal activity in the posterior parietal cortex (PPC). Target-distractor color contrast modulated the late-period activity, whereas stimulus-background luminance contrast modulated the early-period activity. Thus,these results suggest that visual saliency derived from the different types of stimulus contrast is represented with different temporal dynamics in the activity of PPC neurons. doi:10.1016/j.neures.2009.09.1037
P2-o04 Primate prefrontal activities reflects competition among multiple directionally defined choices Kei Watanabe 1,2 , Shintaro Funahashi 1 1
Kokoro Res. Center, Kyoto University Kyoto, Japan; Japan
2
JSPS Res. Fellow,
Previous research implicates the role of DLPFC in free-choice decision processing, in which subjects themselves select what to act in the absence of external instructions. To elucidate its neural mechanism, we examined primate prefrontal activities under two oculomotor delayed-response tasks; the free-choice and instructedchoice tasks. In the free-choice (S-ODR) task, monkeys were required to select, on their own, the direction of saccade among 4 directionally defined alternatives presented as multiple visual cues, while in the instructed-choice (ODR) task, the direction of saccade was externally instructed by a single visual cue. We show that during S-ODR performances, the competition among cue-responsive neurons with different directional preference occurs, thereby generating directional bias relating to the monkeys’ subsequent decision. We propose that at least 2 of hypothetical components that underlie free choice performances, (1) random neuronal fluctuation, (2) influence of past trial history (Haggard, 2008), are reflected in activities of DLPF neurons. doi:10.1016/j.neures.2009.09.1038
P2-o05 Neuronal activity in the primate prefrontal cortex during a metamemory paradigm Akio Tanaka 1 , Shintaro Funahashi 1,2 1 2
Grad. Sch. of Human & Environmental Std., Kyoto University, Japan; Kokoro Res. Ctr., Kyoto University, Japan
The prefrontal cortex (PFC) is known to play crucial roles in working memory processes. To further understand the functional characteristics of prefrontal neurons, we recorded single-neuron activity from the dorsolateral PFC while a monkey performed a modified oculomotor working memory task. In this task, the monkey was sometimes allowed to choose whether to take or escape from a memory test (FrC condition) and was sometimes forced to take the test (FoT condition). The proportion of correct performance was higher in the FrC condition, suggesting that the monkey used an ability to monitor its own memory state when deciding whether or not to take the tests. We observed task-related activities during the cue, delay, and response periods. Some of these neurons exhibited differential activation between the trials in which the monkey chose to take the tests and the trials in which the monkey chose to escape. Detailed analysis of these activities may lead to some insights into the functional roles of prefrontal neurons in the primate memory system. doi:10.1016/j.neures.2009.09.1039
P2-o06 Inactivation of the putamen impairs action value-based selectionbut not estimation of values during multi-step choice task in monkeys Manabu Muranishi 1 , Hitoshi Inokawa 1 , Hiroshi Yamada 2 , Minoru Kimura 1 1 2
Department of Physiology, Kyoto Prefectural University of Medicine, Japan Center for Neural Science, New York University, USA
To examine whether striatal neuron, which is thought to encode action value, contributes to reward based-action selection, we injected muscimol (5 g/l, 2–3 l) into the putamen of a monkey which chose 1 of 3 targets for reward through win-staylose-shift policy. Correct choice rates at first (N1), second (N2), third (N3) choices were 33, 48, 89%, respectively. Once correct button was hit, monkey got another reward by choosing the known button (R1, 96%). Rates of error trials choosing last incorrect buttons again in N2, N3 and R1 trials were 2, 5 and 4%, respectively, before injection, but increased to 5, 32 and 5%, respectively after inactivation of the putamen at anterior commissure level. Monkey could estimate values that did not depend on a choice because behavioral reaction times were changed depending on reward probability after injection, too. When a correct button was illuminated in control task, monkey chose the button without error. These results supported a view that the putamen is involved selectively and critically in reward-based action selection. doi:10.1016/j.neures.2009.09.1040
P2-o07 Model-based and model-free leaning by striatal neurons Xiaochuan Pan, Masamichi Sakagami Brain Science Institute, Tamagawa University, Japan The striatum is the major inputs to basal ganglia and receives afferents from nearly all cortical areas. One of functions for the striatum is thought to be involved in habitual behavior, and apply model-free learning for effortless and fast action selection. To test this hypothesis, we recorded neural activity from the striatum when the monkey performed a sequential paired-association task with asymmetric reward task. The monkey learned two sequences of stimuli: A1-B1-C1 and A2-B2-C2. The asymmetric reward rule was instructed by pairing C1 (or C2) with large (or small) reward block by block. The monkey also learned associations between new stimuli (e.g. N1, N2) and B1 or B2. We found striatal neurons can predict reward based on old stimuli (A1 and A2) just after C1 and C2 were paired with reward. These neurons can not discriminate two reward conditions based on new stimuli just after reward instruction with C1 and C2, but can after directly experiencing new stimulus-reward contingency. Our results suggest that the striatum can perform model-based like method in familiar situations, but only model-free method in novel environments. doi:10.1016/j.neures.2009.09.1041
P2-o08 Prefrontal neurons contribute to temporal filtering in duration discrimination Ken-ichi Oshio, Atsushi Chiba, Masahiko Inase Dept Physiol, Kinki Univ Sch of Med, Osaka-Sayama, Japan It is widely accepted that the prefrontal cortex is a brain area involved in time perception; however, its functional roles remain unclear. We trained two monkeys to perform a duration-discrimination task, in which two visual cues were presented consecutively for different durations ranging from 0.2 to 2.0 s, and subjects were then required to choose the longer cue. Our single-unit recording experiments showed that phasic activity was the most prevailing among responses to the first cue. Peak time of the phasic activity was broadly distributed about 0.8 s after cue onset. The broad distribution of the peak time would indicate that various filtering durations had been prepared for estimating cue duration. The most frequent peak time was close to the time separating cue durations into long and short. The activity with this peak time might have had a role of filtering in attempted duration discrimination. Our results suggest that the prefrontal cortex contributes to duration discrimination with temporal filtering in the cue period. doi:10.1016/j.neures.2009.09.1042
P2-o09 Frontal-parietal synchrony (phase-locking) in human EEG during visual search Steven Phillips, Yuji Takeda The National Institute for Advanced Industrial Science and Technology (AIST), Japan In a monkey study, Buschman and Miller (2007) reported greater frontal-parietal neuronal synchrony in the lower frequency band (22–34 Hz) for conjunctive than feature visual search, but a reverse effect in a higher frequency band (36–56 Hz). We examine whether this difference is also evident in humans using scalp EEG. Analysis of phase-locking values revealed significantly greater synchronization between frontal and parietal electrode pairs in the lower frequency band around 160–480 ms post-stimulus for conjunctive search. No significant difference was observed in the upper frequency band. These results partly correspond to Buschman and Miller (2007), suggesting that top-down control of visual attention is mediated by neuronal synchrony. doi:10.1016/j.neures.2009.09.1043
Abstracts
P2-o03 Neuronal representation of visual saliency in the macaque posterior parietal cortex Tomohiro Tanaka, Atsushi Fujimoto, Tadashi Ogawa Graduate School of Medicine, Kyoto University, Kyoto, Japan A salient stimulus (a red target among green distractors) can automatically attract our attention. To examine neural representation of visual saliency, we trained monkeys to perform a visual search task in which a singleton target was different from distractors in color. We manipulated the degree of visual saliency of the target by independently changing “target-distractor color contrast” and “stimulusbackground luminance contrast”. For the estimation of the degree of visual saliency, we used saccade latency. Both contrasts can modulate saccade latency (when one of the contrasts larger, saccade latency became shorter). We found that these two contrasts differentially modulated neuronal activity in the posterior parietal cortex (PPC). Target-distractor color contrast modulated the late-period activity, whereas stimulus-background luminance contrast modulated the early-period activity. Thus,these results suggest that visual saliency derived from the different types of stimulus contrast is represented with different temporal dynamics in the activity of PPC neurons. doi:10.1016/j.neures.2009.09.1037
P2-o04 Primate prefrontal activities reflects competition among multiple directionally defined choices Kei Watanabe 1,2 , Shintaro Funahashi 1 1
Kokoro Res. Center, Kyoto University Kyoto, Japan; Japan
2
JSPS Res. Fellow,
Previous research implicates the role of DLPFC in free-choice decision processing, in which subjects themselves select what to act in the absence of external instructions. To elucidate its neural mechanism, we examined primate prefrontal activities under two oculomotor delayed-response tasks; the free-choice and instructedchoice tasks. In the free-choice (S-ODR) task, monkeys were required to select, on their own, the direction of saccade among 4 directionally defined alternatives presented as multiple visual cues, while in the instructed-choice (ODR) task, the direction of saccade was externally instructed by a single visual cue. We show that during S-ODR performances, the competition among cue-responsive neurons with different directional preference occurs, thereby generating directional bias relating to the monkeys’ subsequent decision. We propose that at least 2 of hypothetical components that underlie free choice performances, (1) random neuronal fluctuation, (2) influence of past trial history (Haggard, 2008), are reflected in activities of DLPF neurons. doi:10.1016/j.neures.2009.09.1038
P2-o05 Neuronal activity in the primate prefrontal cortex during a metamemory paradigm Akio Tanaka 1 , Shintaro Funahashi 1,2 1 2
Grad. Sch. of Human & Environmental Std., Kyoto University, Japan; Kokoro Res. Ctr., Kyoto University, Japan
The prefrontal cortex (PFC) is known to play crucial roles in working memory processes. To further understand the functional characteristics of prefrontal neurons, we recorded single-neuron activity from the dorsolateral PFC while a monkey performed a modified oculomotor working memory task. In this task, the monkey was sometimes allowed to choose whether to take or escape from a memory test (FrC condition) and was sometimes forced to take the test (FoT condition). The proportion of correct performance was higher in the FrC condition, suggesting that the monkey used an ability to monitor its own memory state when deciding whether or not to take the tests. We observed task-related activities during the cue, delay, and response periods. Some of these neurons exhibited differential activation between the trials in which the monkey chose to take the tests and the trials in which the monkey chose to escape. Detailed analysis of these activities may lead to some insights into the functional roles of prefrontal neurons in the primate memory system. doi:10.1016/j.neures.2009.09.1039
P2-o06 Inactivation of the putamen impairs action value-based selectionbut not estimation of values during multi-step choice task in monkeys Manabu Muranishi 1 , Hitoshi Inokawa 1 , Hiroshi Yamada 2 , Minoru Kimura 1 1 2
Department of Physiology, Kyoto Prefectural University of Medicine, Japan Center for Neural Science, New York University, USA
To examine whether striatal neuron, which is thought to encode action value, contributes to reward based-action selection, we injected muscimol (5 g/l, 2–3 l) into the putamen of a monkey which chose 1 of 3 targets for reward through win-staylose-shift policy. Correct choice rates at first (N1), second (N2), third (N3) choices were 33, 48, 89%, respectively. Once correct button was hit, monkey got another reward by choosing the known button (R1, 96%). Rates of error trials choosing last incorrect buttons again in N2, N3 and R1 trials were 2, 5 and 4%, respectively, before injection, but increased to 5, 32 and 5%, respectively after inactivation of the putamen at anterior commissure level. Monkey could estimate values that did not depend on a choice because behavioral reaction times were changed depending on reward probability after injection, too. When a correct button was illuminated in control task, monkey chose the button without error. These results supported a view that the putamen is involved selectively and critically in reward-based action selection. doi:10.1016/j.neures.2009.09.1040
P2-o07 Model-based and model-free leaning by striatal neurons Xiaochuan Pan, Masamichi Sakagami Brain Science Institute, Tamagawa University, Japan The striatum is the major inputs to basal ganglia and receives afferents from nearly all cortical areas. One of functions for the striatum is thought to be involved in habitual behavior, and apply model-free learning for effortless and fast action selection. To test this hypothesis, we recorded neural activity from the striatum when the monkey performed a sequential paired-association task with asymmetric reward task. The monkey learned two sequences of stimuli: A1-B1-C1 and A2-B2-C2. The asymmetric reward rule was instructed by pairing C1 (or C2) with large (or small) reward block by block. The monkey also learned associations between new stimuli (e.g. N1, N2) and B1 or B2. We found striatal neurons can predict reward based on old stimuli (A1 and A2) just after C1 and C2 were paired with reward. These neurons can not discriminate two reward conditions based on new stimuli just after reward instruction with C1 and C2, but can after directly experiencing new stimulus-reward contingency. Our results suggest that the striatum can perform model-based like method in familiar situations, but only model-free method in novel environments. doi:10.1016/j.neures.2009.09.1041
P2-o08 Prefrontal neurons contribute to temporal filtering in duration discrimination Ken-ichi Oshio, Atsushi Chiba, Masahiko Inase Dept Physiol, Kinki Univ Sch of Med, Osaka-Sayama, Japan It is widely accepted that the prefrontal cortex is a brain area involved in time perception; however, its functional roles remain unclear. We trained two monkeys to perform a duration-discrimination task, in which two visual cues were presented consecutively for different durations ranging from 0.2 to 2.0 s, and subjects were then required to choose the longer cue. Our single-unit recording experiments showed that phasic activity was the most prevailing among responses to the first cue. Peak time of the phasic activity was broadly distributed about 0.8 s after cue onset. The broad distribution of the peak time would indicate that various filtering durations had been prepared for estimating cue duration. The most frequent peak time was close to the time separating cue durations into long and short. The activity with this peak time might have had a role of filtering in attempted duration discrimination. Our results suggest that the prefrontal cortex contributes to duration discrimination with temporal filtering in the cue period. doi:10.1016/j.neures.2009.09.1042
P2-o09 Frontal-parietal synchrony (phase-locking) in human EEG during visual search Steven Phillips, Yuji Takeda The National Institute for Advanced Industrial Science and Technology (AIST), Japan In a monkey study, Buschman and Miller (2007) reported greater frontal-parietal neuronal synchrony in the lower frequency band (22–34 Hz) for conjunctive than feature visual search, but a reverse effect in a higher frequency band (36–56 Hz). We examine whether this difference is also evident in humans using scalp EEG. Analysis of phase-locking values revealed significantly greater synchronization between frontal and parietal electrode pairs in the lower frequency band around 160–480 ms post-stimulus for conjunctive search. No significant difference was observed in the upper frequency band. These results partly correspond to Buschman and Miller (2007), suggesting that top-down control of visual attention is mediated by neuronal synchrony. doi:10.1016/j.neures.2009.09.1043