Attentional Mechanisms in Visual Processing

Our attention is selective because we cannot process all stimuli in a scene simultaneously. We prioritize important or task-related information.

Kahneman's theory suggested that our capacity for information processing is limited.

We have a finite amount of mental resources available for processing information.

When presented with too much information, it overwhelms our cognitive processing abilities.

The current view is that sensory perception is complex because the brain needs to combine information processed in different areas.

Temporal

Parietal

Different parts of the brain process individual features of a stimulus, but these features must be combined for us to perceive a whole object.

There is competition between various stimuli for representation in the visual cortex.

1. Stimuli compete for control of neuronal responses.
2. Top-down or bottom-up mechanisms influence this competition.
3. Attention integrates these objects to overcome the binding problem.

Monkeys were presented with effective and ineffective sensory stimuli either within the visual field or with one outside it. Neuronal activity in the visual cortex was measured during tasks involving visual spatial attention.

Stimuli compete for control of neurons. However, unattended features are filtered out from the receptive fields.

Humans were shown stimuli sequentially and simultaneously while being asked to passively attend or attend to a specific location.

When stimuli were presented simultaneously, V4 BOLD activity was reduced compared to sequential presentation. However, attending to the stimulus location recovered V4 BOLD activity simultaneously to levels seen in sequential presentation.

Different regions of the visual cortex are specialized for processing information at different scales, whether it's small details or large-scale patterns.

V4

LOC

Participants were cued with an indication of whether a movement or color trial would follow, allowing them to prepare for the specific task.

When attending to color, increased activity was observed in V4. When attending to motion, increased activity was observed in MT.

Participants attended to either static or moving faces or houses, with the images superimposed on each other.

When attending to faces, whether stationary or moving, the fusiform face area (FFA) showed higher BOLD activity. When attending to houses, the parahippocampal area showed increased BOLD activity.

Participants were cued with a stimulus, then a delay period followed, after which the target stimulus and a distractor appeared. They had to saccade their eyes toward the target.

Attention increased the baseline firing rate of neurons during the delay for neurons that preferred the cued stimulus.

Participants were shown target and non-target stimuli.

Prior to stimulus presentation, participants showed shape-specific activity when anticipating the outcome.

It refers to the influence of the frontoparietal attention network on sensory processing, guiding our focus.

Damage to the prefrontal cortex (PFC) alters visual processing, affecting how we attend to visual information.

Both PFC lesion patients and control participants were able to attend to targets.

PFC lesion patients showed reduced visual evoked ERP responses to the attended stimuli in the visual cortex.

Monkeys performed an attention task while undergoing microstimulation of the FEF (frontal eye field) and single-unit recordings from the visual area V4.

Stimulation improved the monkeys' ability to detect changes, suggesting a crucial role for the FEF in attention.

Participants were cued for either motion or face gender. Transcranial magnetic stimulation (TMS) was applied to the FEF, and EEG signals were recorded.

TMS caused increased activity in the MT during motion tasks and in the FFA during face-cued trials.