Active inhibition of task-irrelevant sounds and its neural basis in patients with attention deficits after traumatic brain injury

Daisuke Sawamura, Katsunori Ikoma, Kazuki Yoshida, Yuji Inagaki, Keita Ogawa, Shinya Sakai
2014 Brain Injury  
Primary objective: To examine active inhibition of irrelevant stimuli and evaluate its neural basis using functional near infrared spectroscopy in patients with attention deficits after traumatic brain injury (TBI). Research Design: case control study. Methods and procedures: Ten patients with TBI and 10 healthy control subjects participated in this study. The Paced Auditory Serial Addition Test (PASAT) was performed with (distracting PASAT) and without (PASAT) distracting Japanese kana
more » ... panese kana phonetic characters presented between each number. A block design was used. Subjects alternately performed each task three times. Main outcomes and results: Healthy controls performed better than patients with TBI on both the tasks. When performing the PASAT, healthy controls showed significant activity in every region of interest except the right lateral prefrontal cortex (PFC), but patients with TBI showed significant activity only in the left anterior PFC and left lateral PFC. When performing the distracting PASAT, the right lateral PFC was active in healthy controls, but not in patients with TBI. Conclusion: These results confirm that patients with moderate-to-severe TBI were affected by distractors that influenced order processing. We suggest that the working memory of patients with TBI was affected by distracting stimuli, whereas that of healthy individuals was not. Introduction On a daily basis, we are exposed to a variety of environmental sounds such as conversations, air-conditioning equipment, and cars. These environmental sounds do not cause a salient decline in the performance of everyday tasks, and even if they temporarily capture our attention we can easily return to the ongoing task. This is because, when engaging in a task, humans are insulated against unnecessary information such as noise so that attention can be focused on necessary information. Such control of attention is called active inhibition, and it plays an important role in the maintenance of task performance [1,2]. However, patients with attention deficits after traumatic brain injury (TBI) find it difficult to filter out irrelevant auditory stimuli, even when they must concentrate on a task. Therefore, they are easily distracted by any auditory stimuli in their surroundings and have trouble carrying out tasks [3, 4] . Working memory tasks such as serial recall of numbers and words are frequently used in applied psychology, and some studies have reported that performance of these tasks was reduced by task-irrelevant sounds or speech [5, 6] . The degree of disruption varied with the task difficulty (cognitive load) and the characteristics of the distraction [5, 7] . The effect of distractors on task performance and the neural basis of active inhibition are not necessarily the same in patient populations as in healthy subjects. For instance, Söderlund et al. [8] reported that performance of a short-term memory task improved in the presence of distracting stimuli in patients with attention deficit hyperactivity disorder. The effect of distractors on task performance and the neural basis of active inhibition may also differ between patients with TBI and healthy individuals, but there are no functional brain imaging studies on the effect of auditory distractors on task performance or the neural basis of active inhibition in patients with TBI. Active inhibition involves two functionally distinct cognitive processes: working memory and order processing [5] . In inhibition processes that involve working memory there is active inhibition of unexpected distractors (e.g., sudden sounds) with attention capture (deviation effect) and of distractors with semantic
doi:10.3109/02699052.2014.919531 pmid:24946201 fatcat:kqgtoitxmfhivah2ltgsmrlyga