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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.

It has been reported that neurons in the orbitofrontal cortex respond to visual cues that predict reward; however, few studies have focused on the neuronal correlates with the predicted reward type and the cue stimulus. In this study, we used a paired association task and introduced a reversal condition, in which cue stimuli that usually predict water were switched to predict juice, and vice versa. Of 111 cue-responsive neurons, 60 neurons (54.1%) depended on both the cue stimulus and the predicted reward type. The results suggest that neurons in the orbitofrontal cortex can code both visual and reward information, and contribute to the association between these two pieces of information according to the current combination of a cue stimulus and a reward type.

We examined cortical activation by speech in patients with moderate inner ear hearing loss using PET to investigate the response of the language network to insufficient speech input. We made two word lists, well-perceived words and poorly-perceived words, and measured rCBF during monaural presentation of these words. Well-perceived words activated bilateral temporal lobes, bilateral inferior frontal gyri (IFG) and left angular gyrus (AG) regardless of the ear stimulated, Poorly-perceived words activated contralateral temporal lobe and bilateral IFG, while little or no activation was observed in the ipsilateral temporal lobe and left AG. Insufficient activation of the temporal lobe ipsilateral to the ear stimulated might correlated with less accurate word comprehension in patients with inner ear hearing loss.

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.

To examine interactions between primate prefrontal neurons having memory fields, we examined whether primate prefrontal delay-period activity produced by a visual cue presented inside the neuron's memory field is affected by an additional visual cue presented inside or outside the memory field in 39 prefrontal neurons. Delay-period activity was either diminished (43%) or enhanced (16%) when an additional cue was presented at a certain area in the visual field. Since functional interactions among neighboring prefrontal neurons were present, these modulation could be caused by the interactions between neurons having memory fields in different positions.