In patients with MS, dysfunctional visual search behavior may be one of the mechanisms that translate cognitive deficits into difficulties performing everyday tasks.


 

In patients with multiple sclerosis, the precise mechanism underlying the translation of cognitive dysfunction into difficulties in everyday tasks remains unclear, according to the authors of a study published in Frontiers in Neurology. “We hypothesized that patients with MS with low [Symbol Digit Modalities Test (SDMT)] scores would need more time to fixate the location of the target object, as this reflects processing speed and the integrity of top-down processes such as expectations and prior knowledge that determine where to search for a target object,” they wrote. The study team also expected less efficient search behavior in patients with cognitive impairment to be linked with a larger amount of fixations of non-target areas prior to the first fixation of the target and a shorter total fixation duration compared with patients who are cognitively preserved.

 

Visual Search Strongly Driven by Top-Down Cognitive Processes

For their study, the researchers tested these hypotheses by investigating if patients with MS with intact versus impaired information processing speed differ in their visual search behavior while performing everyday activities. They enrolled 43 patients with relapsing-remitting MS (RRMS) in an eye-tracking experiment consisting of a visual search task with naturalistic images. Patients were grouped into “impaired” and “unimpaired” based on their SDMT performance. Measurements were taken of reaction time, accuracy, and eye-tracking parameters.

The groups did not differ regarding age, gender, and visual acuity. Patients who were impaired (SDMT z < −1.5) were less accurate in indicating whether the searched object was present or not and needed more reaction time, suggesting that visual search in naturalistic scenes is strongly driven by top-down cognitive processes.

 

Visual Search in Patients With Cognitive Impairment Less Efficient

Patients who were unimpaired showed higher accuracy than patients who were impaired, particularly when the target was in an unexpected location. Correlational analysis suggested that SDMT performance is inversely associated with the time to first fixation of the target only if the target is in its expected location (r = −0.498 vs r = −0.212).

In patients with MS, dysfunctional visual search behavior may be one of the mechanisms that translate cognitive deficits into difficulties performing everyday tasks, according to the study authors. “Our results suggest that patients with cognitively impairment search their visual environment less efficiently and this is particularly evident when top-down processes have to be employed,” the wrote.