2015年6月29日月曜日

Orbitofrontal lesions eliminate signalling of biological significance in cue-responsive ventral striatal neurons

Nisha K. Cooch, Thomas A. Stalnaker, Heather M. Wied, Sheena Bali-Chaudhary, Michael A. McDannald, Tzu-Lan Liu & Geoffrey Schoenbaum
Nature Communications 6, Article number: 7195

ラットの腹側線条体(ventral striatum)は「報酬を示す手掛かり刺激」に対してその報酬量に比例して反応することが知られているが、眼窩前頭前野(orbitofrontal cortex, OFC)を破壊すると、手掛かり刺激そのものには反応するがその報酬量への反応は消える。

The ventral striatum has long been proposed as an integrator of biologically significant associative information to drive actions. Although inputs from the amygdala and hippocampus have been much studied, the role of prominent inputs from orbitofrontal cortex (OFC) are less well understood. Here, we recorded single-unit activity from ventral striatum core in rats with sham or ipsilateral neurotoxic lesions of lateral OFC, as they performed an odour-guided spatial choice task. Consistent with prior reports, we found that spiking activity recorded in sham rats during cue sampling was related to both reward magnitude and reward identity, with higher firing rates observed for cues that predicted more reward. Lesioned rats also showed differential activity to the cues, but this activity was unbiased towards larger rewards. These data support a role for OFC in shaping activity in the ventral striatum to represent the biological significance of associative information in the environment.

2015年6月26日金曜日

A Sensitive and Specific Neural Signature for Picture-Induced Negative Affect

Chang LJ, Gianaros PJ, Manuck SB, Krishnan A, Wager TD (2015)
PLoS Biol 13(6): e1002180.

写真を見た際の(負の)感情評価を「全脳のボクセルを対象にしたfMRI MVPA(実際に効いているのは全ボクセルの1.6%)」を用いて高精度(正解率90%以上)に予測できる。 http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002180

Neuroimaging has identified many correlates of emotion but has not yet yielded brain representations predictive of the intensity of emotional experiences in individuals. We used machine learning to identify a sensitive and specific signature of emotional responses to aversive images. This signature predicted the intensity of negative emotion in individual participants in cross validation (n =121) and test (n = 61) samples (high–low emotion = 93.5% accuracy). It was unresponsive to physical pain (emotion–pain = 92% discriminative accuracy), demonstrating that it is not a representation of generalized arousal or salience. The signature was comprised of mesoscale patterns spanning multiple cortical and subcortical systems, with no single system necessary or sufficient for predicting experience. Furthermore, it was not reducible to activity in traditional “emotion-related” regions (e.g., amygdala, insula) or resting-state networks (e.g., “salience,” “default mode”). Overall, this work identifies differentiable neural components of negative emotion and pain, providing a basis for new, brain-based taxonomies of affective processes.

2015年6月25日木曜日

Signatures of Value Comparison in Ventral Striatum Neurons

Strait CE, Sleezer BJ, Hayden BY (2015)
PLoS Biol 13(6): e1002173.

価値に基づく意思決定において、腹側線条体と腹内側前頭前野のニューロンは同じような報酬情報をコードしている。 http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002173

The ventral striatum (VS), like its cortical afferents, is closely associated with processing of rewards, but the relative contributions of striatal and cortical reward systems remains unclear. Most theories posit distinct roles for these structures, despite their similarities. We compared responses of VS neurons to those of ventromedial prefrontal cortex (vmPFC) Area 14 neurons, recorded in a risky choice task. Five major response patterns observed in vmPFC were also observed in VS: (1) offer value encoding, (2) value difference encoding, (3) preferential encoding of chosen relative to unchosen value, (4) a correlation between residual variance in responses and choices, and (5) prominent encoding of outcomes. We did observe some differences as well; in particular, preferential encoding of the chosen option was stronger and started earlier in VS than in vmPFC. Nonetheless, the close match between vmPFC and VS suggests that cortex and its striatal targets make overlapping contributions to economic choice.