Color Working Memory Research Articles

Infants' visual working memory for shape, luminance and color tested with equally salient objects

Infants' visual working memory for shape, luminance and color tested with equally salient objects

Effects of decay and interference on visual working memory for color

Effects of decay and interference on visual working memory for color

Brain activation and deactivation during location and color working memory tasks in 11–13-year-old children

Using functional magnetic resonance imaging (fMRI) and n-back tasks we investigated whether, in 11–13-year-old children, spatial (location) and nonspatial (color) information is differentially processed during visual attention (0-back) and working memory (WM) (2-back) tasks and whether such cognitive task performance, compared to a resting state, results in regional deactivation. The location 0-back task, compared to the color 0-back task, activated segregated areas in the frontal, parietal and occipital cortices whereas no differentially activated voxels were obtained when location and color 2-back tasks were directly contrasted. Several midline cortical areas were less active during 0- and 2-back task performance than resting state. The task-induced deactivation increased with task difficulty as demonstrated by larger deactivation during 2-back than 0-back tasks. The results suggest that, in 11–13-year-old children, the visual attentional network is differently recruited by spatial and nonspatial information processing, but the functional organization of cortical activation in WM in this age group is not based on the type of information processed. Furthermore, 11–13-year-old children exhibited a similar pattern of cortical deactivation that has been reported in adults during cognitive task performance compared to a resting state.

Dynamic Synchrony of Firing in the Monkey Prefrontal Cortex during Working-Memory Tasks

Synchronized firing among neurons in the working brain is inferred to reflect coding by cell assemblies, which dynamically change their sizes and functional connections to encode various information. It therefore follows that, if synchronized firing reflects cell-assembly coding, it should show dynamic changes that depend on the tasks and events being processed and on the distance between the neurons. By using unique spike-sorting and multi-neuronal recording methods, we investigated such dynamics of synchrony in the prefrontal cortex of monkeys while they were successively performing two tasks in which working memory for either stimulus duration or color was required. Forty-eight percent of 1405 neuronal pairs showed firing synchrony during the performance of the tasks. Almost half of such neuronal pairs showed fixed synchrony and constantly fired together in both tasks. However, some neuronal pairs showed task-dependent synchrony that appeared in only one of the tasks. Moreover, the other neuronal pairs showed event-task-dependent synchrony that appeared during stimulus or retention periods in the tasks, but the periods showing synchrony varied between the tasks. Fixed synchrony and task-dependent synchrony were mostly observed among neighboring neurons and showed little variation of spike timings; the event-task-dependent synchrony, in contrast, was more often detected among distant neurons with larger variation of spike timings than the other two types of synchrony. These results suggest that some closely neighboring neurons have dynamic and sharp synchrony to represent certain situations (tasks), whereas some distant neurons show more dynamic and unstable synchronous firing to represent quickly changing events being processed in working memory.

Spatial and color working memory in patients with lateral prefrontal cortex lesions

Lateral prefrontal cortex (LPFC) has previously been associated with both attention and working memory. To study both of these mechanisms, patients with LPFC lesions and age-matched controls were tested on working memory tasks that included an interference condition. On a spatial working memory task, patients were impaired overall relative to controls in both no-interference and interference conditions. There was also a significant correlation between patients’ performance and the extent of damage to Area 46. Participants were also tested on a color working memory paradigm, in which they had to remember an object’s color, rather than location. LPFC patients were disproportionately impaired in the interference condition of this experiment—namely, when they had to perform an interference task during the delay period of the color working memory task. These results are discussed with respect to previous animal and human studies of attention and working memory.

INTERFERENCE FACTORS IN DELAYED RESPONSE IN MONKEYS AFTER REMOVAL OF FRONTAL LOBES

INTERFERENCE FACTORS IN DELAYED RESPONSE IN MONKEYS AFTER REMOVAL OF FRONTAL LOBES