Dynamic Integration of Task-Relevant Visual Features in Posterior Parietal Cortex

Abstract

Summary The primate visual system consists of multiple hierarchically organized cortical areas, each specialized for processing distinct aspects of the visual scene. For example, color and form are encoded in ventral pathway areas such as V4 and inferior temporal cortex, while motion is preferentially processed in dorsal pathway areas such as the middle temporal area. Such representations often need to be integrated perceptually to solve tasks which depend on multiple features. We tested the hypothesis that the lateral intraparietal area (LIP) integrates disparate task-relevant visual features by recording from LIP neurons in monkeys trained to identify target stimuli composed of conjunctions of color and motion features. We show that LIP neurons exhibit integrative representations of both color and motion features when they are task relevant, and task-dependent shifts of both direction and color tuning. This suggests that LIP plays a role in flexibly integrating task-relevant sensory signals.

Task-specific versus generalized mnemonic representations in parietal and prefrontal cortices

“…This is consistent with previous reports of LIP direction tuning during both passive viewing and complex tasks 33,34 , and likely reflects LIP’s interconnection with upstream motion processing areas such as MT, the medial superior temporal (MST) 35 , and the ventral intraparietal 36–38 . Interestingly a recent study using a variant of a motion direction DMS task found delay-period direction encoding in MST but not MT 39 .…”

Interaction between Spatial and Feature Attention in Posterior Parietal Cortex

“…FBA affects LIP neurons in a spatially global manner as feature tuning shifts toward the relevant features, consistent with our earlier report (Ibos and Freedman, 2014), were qualitatively independent of the spatial position of attention. However, SBA modulated FBA effects as the amplitudes of feature-tuning shifts were larger when behaviorally-relevant stimuli were located inside neurons’ RFs.…”

“…SBA or FBA have both been shown to enhance encoding of task relevant locations or features throughout the visual cortical hierarchy (Cohen and Maunsell, 2011; Connor et al, 1997; Ipata et al, 2012; Martinez-Trujillo and Treue, 2004; Maunsell and Treue, 2006) as well as higher order areas such as the Lateral Intraparietal (LIP) area (Bisley and Goldberg, 2010; Herrington and Assad, 2009; Ibos and Freedman, 2014), frontal-eye field (FEF) (Armstrong et al, 2009; Ibos et al, 2013; Zhou and Desimone, 2011) and prefrontal cortex (PFC) (Bichot et al, 2015; Hussar and Pasternak, 2013; Lennert and Martinez-Trujillo, 2011, 2013; Tremblay et al, 2015). Moreover, the impact of SBA and FBA on the response of visual cortical neurons suggests that both types of attention modulate neuronal processing in similar ways (Cohen and Maunsell, 2009, 2011; Hayden and Gallant, 2009; Leonard et al, 2015).…”

“…LIP is a core node in the network of brain areas mediating attention. For example, recordings from LIP during a wide range of tasks show strong modulations of neuronal activity due to both SBA (Bisley and Goldberg, 2010; Herrington and Assad, 2009; Saalmann et al, 2007) and FBA (Ibos and Freedman, 2014). However, the extent to which LIP plays a central role in generating attentional modulations, or receives attentional control signals from other brain areas remains unclear.…”

“…On the other hand, we recently proposed that FBA modulations of LIP activity reflect the bottom-up integration of attentional modulations of upstream visual areas (e.g. V4 or MT) (Ibos and Freedman, 2014), in order to enhance the representation of task-relevant features and to facilitate decision-making. This apparent dichotomy between LIP being either an “emitter” of SBA signals or a “receiver” of FBA modulations raises a question about the precise role of LIP in attentional control.…”