A Quadrantic Bias in Prefrontal Representation of Visual-Mnemonic Space

TY - JOUR

T1 - A Quadrantic Bias in Prefrontal Representation of Visual-Mnemonic Space

AU - Leavitt, Matthew

AU - Pieper, Florian

AU - Sachs, Adam

AU - Martinez-Trujillo, Julio C

PY - 2018/7/1

Y1 - 2018/7/1

N2 - Single neurons in primate dorsolateral prefrontal cortex (dLPFC) are known to encode working memory (WM)representations of visual space. Psychophysical studies have shown that the horizontal and vertical meridians of the visualfield can bias spatial information maintained in WM. However, most studies and models have tacitly assumed that dLPFCneurons represent mnemonic space homogenously. The anatomical organization of these representations has also eludedclear parametric description. We investigated these issues by recording from neuronal ensembles in macaque dLPFC withmicroelectrode arrays while subjects performed an oculomotor delayed-response task. We found that spatial WMrepresentations in macaque dLPFC are biased by the vertical and horizontal meridians of the visual field, dividingmnemonic space into quadrants. This bias is reflected in single neuron firing rates, neuronal ensemble representations, thespike count correlation structure, and eye movement patterns. We also found that dLPFC representations of mnemonicspace cluster anatomically in a nonretinotopic manner that partially reflects the organization of visual space. These resultsprovide an explanation for known WM biases, and reveal novel principles of WM representation in prefrontal neuronalensembles and across the cortical surface, as well as the need to reconceptualize models of WM to accommodate theobserved representational biases.

AB - Single neurons in primate dorsolateral prefrontal cortex (dLPFC) are known to encode working memory (WM)representations of visual space. Psychophysical studies have shown that the horizontal and vertical meridians of the visualfield can bias spatial information maintained in WM. However, most studies and models have tacitly assumed that dLPFCneurons represent mnemonic space homogenously. The anatomical organization of these representations has also eludedclear parametric description. We investigated these issues by recording from neuronal ensembles in macaque dLPFC withmicroelectrode arrays while subjects performed an oculomotor delayed-response task. We found that spatial WMrepresentations in macaque dLPFC are biased by the vertical and horizontal meridians of the visual field, dividingmnemonic space into quadrants. This bias is reflected in single neuron firing rates, neuronal ensemble representations, thespike count correlation structure, and eye movement patterns. We also found that dLPFC representations of mnemonicspace cluster anatomically in a nonretinotopic manner that partially reflects the organization of visual space. These resultsprovide an explanation for known WM biases, and reveal novel principles of WM representation in prefrontal neuronalensembles and across the cortical surface, as well as the need to reconceptualize models of WM to accommodate theobserved representational biases.

U2 - 10.1093/cercor/bhx142

DO - 10.1093/cercor/bhx142

M3 - SCORING: Journal article

VL - 28

SP - 2405

EP - 2421

JO - CEREB CORTEX

JF - CEREB CORTEX

SN - 1047-3211

IS - 7

ER -