What it is
Neurons throughout the brain encode essentially everything, so the authors asked why distinct areas exist, proposing that areas differ in how they format information. Two rhesus monkeys reported the direction of moving dots with an eye movement to a ring, earning juice that depended on their accuracy and on a reward scaling marked on the ring, over 27 sessions and 41,106 choices. Recording at the same time from the middle temporal area (MT), involved in visual motion perception, and the dorsolateral prefrontal cortex (dlPFC), implicated in decision-making and reward, in 15 sessions (258 MT units and 322 dlPFC units), they found that both areas encoded both motion and reward, but formatted differently: MT represented them separably, while the dlPFC combined them in a decision-related format. A recurrent network model trained to reproduce that formatting predicted that stimulating the two areas would affect choices differently, and electrical microstimulation agreed. In MT (50 sites over 29 sessions) it biased choices midway between the motion direction and the stimulated site's preference; in the dlPFC (38 sites over 23 sessions) the monkeys reported either the motion or the site's preference, a 'winner-take-all' outcome with no evidence of averaging.
Why it matters
A brain area's role may be read from how it formats what it encodes, not only from what it encodes, and here that format predicted what stimulating the area would do. The prediction went beyond the shape of the choices: the effect of dlPFC stimulation was much greater when the larger reward sat at the stimulated site's preferred direction, while the effect of MT stimulation was indistinguishable between the two reward conditions, consistent with joint and separable representations. The authors suggest that a modular structure flexibly reformats information to enable complex behaviours.
Underlined numbers link to their source. Every metric and quoted figure is listed under Sources and data below.
Filed underNeural dynamics and brain function, Visual perception and processing mechanisms, Neural and Behavioral Psychology Studies
