Prefrontal cortex is critical for contextual processing: evidence from brain lesions

Abstract

We investigated the role of prefrontal cortex (PFC) in local contextual processing using a combined event-related potentials and lesion approach. Local context was defined as the occurrence of a short predictive series of visual stimuli occurring before delivery of a target event. Targets were preceded by either randomized sequences of standards or by sequences including a three-stimulus predictive sequence signalling the occurrence of a subsequent target event. PFC lesioned patients were impaired in their ability to use local contextual information. The response time for controls revealed a larger benefit for predictable targets than for random targets relative to PFC patients. PFC patients had reduced amplitude of a context-dependent positivity and failed to generate the expected P3b latency shift between predictive and non-predictive targets. These findings show that PFC patients are unable to utilize predictive local context to guide behaviour, providing evidence for a critical role of PFC in local contextual processing.

Prefrontal cortex modulates posterior alpha oscillations during top-down guided visual perception

“…We did not observe an interaction of prediction and rhythmic stimulation, which implies a functional separation of top-down and bottomup systems supporting visual perception. Our results are in accordance with previous lesion studies, which indicated that high-level visual perception is PFC dependent (27,31), as well as reports suggesting that long-range endogenous delta activity may constitute a neural correlate of directed top-down control (15). For example, Johnson et al (31) reported that prefrontal damage diminished long-range top-down control that was associated with oscillatory activity in the delta-theta range (2-7 Hz).…”

“…The last three items of the stream could either carry the predictive sequence (clockwise rotating triangles) (27) or not (Fig. 1A).…”

“…1A), we manipulated the bottom-up sensory evidence by titrating the target luminance to perceptual threshold as well as the degree of high-level top-down predictions (27). Previously, it had been demonstrated that patients with prefrontal cortex (PFC) lesions were unable to use a predictive visual sequence (clockwise left-, up-, rightward facing triangles) in this task to guide behavior, suggesting a key role of the PFC in using predictive information (27). Importantly, in the current study the visual stream was presented either arrhythmically or at 10 Hz to drive cortical alpha activity in a bottom-up manner, but the visual stream did not contain temporal information about the upcoming target.…”

Analysis of the cerebral mechanisms underlying rehabilitation of the patients after stroke

“…Допамин модулирует корти-кальные нейронные сети, поддерживая оператив-ную память и моторные функции через 2 различных механизма: нигростриальные проекции потенциру-ют моторную функцию не напрямую, а через тала-мические проекции на моторную кору, тогда как мезокортикальная допаминергическая система по-тенцирует функцию оперативной памяти и внима-ния через прямой вход в префронтальную кору. Это обеспечивает прямой путь, посредством которого допаминергические «входы» воздействуют на пре-фронтальную кору и влияют на мозговой процес-синг (функцию обработки временной информации) [11,[23][24][25][26].…”

“…Временными интервалами от секунд до минут измеряется время принятия решения, в то время как миллисекунды требуются для осущест-вления центрального моторного контроля, воспри-ятия и реализации экспрессивной речи, музыкаль-ной игры или танцев [24]. Ранее предполагалось, что временной процессинг миллисекундных и секунд-ных временных интервалов может зависеть от раз-личных нейронных сетей и относительно независи-мых друг от друга мозговых механизмов.…”