Neural measures of dynamic changes in attentive tracking load

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Electrophysiology

Background:

• Everyday tasks require tracking multiple objects, a process modeled by the multiple-object tracking (MOT) task.
• Unlike standard MOT, real-world tracking involves a fluid set of relevant targets that change over time.
• Humans effectively manage dynamic changes in tracked object sets.

Purpose of the Study:

• To investigate the neural underpinnings of dynamically updating visual attention during multiple object tracking.
• To determine if the contralateral delay activity (CDA) reflects the current number of attended objects or a dynamic tracking load.
• To measure on-line changes in CDA amplitude in response to cues altering the number of tracked objects.

Main Methods:

• Electrophysiological methods were used to measure brain activity.
• The contralateral delay activity (CDA), a sustained lateralized negativity, was recorded.
• Participants responded to 'add' or 'drop' cues to dynamically alter the number of tracked objects within a trial.

Main Results:

• CDA amplitude dynamically changed in response to cues that modified the number of tracked objects.
• The CDA signal appears to rapidly represent the current number of objects being attended.
• Initial estimates of the time course for these dynamic CDA changes were generated.

Conclusions:

• The contralateral delay activity (CDA) is a dynamic neural signal that reflects real-time changes in visual tracking load.
• This finding extends previous work showing CDA indexes working memory capacity and static MOT load.
• The CDA provides a measure of the brain's ability to adjust attentional focus as the number of tracked objects changes dynamically.