Distractibility When Suffering from Mental Fatigue after a Mild Traumatic Brain Injury

Research Article

Phys Med Rehabil Int. 2021; 8(3): 1184.

Distractibility When Suffering from Mental Fatigue after a Mild Traumatic Brain Injury

Johansson B*

Institute of Neuroscience and Physiology, University of Gothenburg, Sweden

*Corresponding author: Birgitta Johansson, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Blå Stråket 7, v3, 413 45 Göteborg, Sweden

Received: June 23, 2021; Accepted: August 03, 2021; Published: August 10, 2021


Most Traumatic Brain Injuries are mild (mTBI) yet many people suffer from long-term mental fatigue and cognitive impairment. Despite comments from patients, cognitive difficulties can go undetected. Distractibility is commonly reported but is seldom included in standard neuropsychological assessment. This study was designed to investigate the effect distraction may induce in topdown and bottom-up attention among people who suffer from mental fatigue after mTBI. Thirty mTBI patients suffering from mental fatigue and 30 healthy controls performed a computerized test, including Simple Reaction Time, Choice Reaction Time and Attentional Capture tasks with a salient distractor. A slower processing speed was found in all subtests for the mTBI group and was particularly noticeable for the decision-making task. The distraction stimulus reduced processing speed for both groups, while the mTBI group made more omissions when a distractor emerged, indicating increased distractibility. However, no effect in top-down and bottom-up attention was found. Response time in the presence of a distractor was a predictor for mental fatigue, while depression and anxiety were not, showing the importance to carefully distinguish between emotional distress and mental fatigue. In conclusion, it is suggested that people suffering from mental fatigue after mTBI are slower at processing information, and this is more pronounced when a cognitive demand is added to the task. Distractibility was indicated with more omissions during distraction, but a distinction between top-down and bottom-up systems was not found. Further research is needed to better understand the link between distractibility and mental fatigue after a brain injury.

Keywords: Mild TBI; Mental fatigue; Distractibility; Attention; Processing speed


People of all ages can suffer a Traumatic Brain Injury (TBI) and approximately 70-90% of these are mild TBI (mTBI) [1]. Many recover within one to three months but not all and among trafficrelated mTBI 23% did not recover within a year [2]. From a study performed in the Netherlands an unfavorable outcome was reported for 30% of all mTBI patients [3]; from a review approximately half of the individuals with a single mTBI demonstrated long-term cognitive impairment [4]. The estimation varies depending on definition of mTBI and outcome measures. At all events, it is clear that longterm difficulties can persist after an mTBI. More importantly for the individual are the consequences for everyday life and it has been shown that long-term cognitive impairment after an mTBI is related to reduce community participation [5].

For those patients with insufficient recovery after mTBI, pathological mental fatigue is common having impact on well-being and quality of life [6]. From a longitudinal study only 27% recovered an mTBI within the first year; the most common symptoms reported were headache, difficulty concentrating and fatigue [7]. It has been proposed that fatigue after TBI correlates with poor performance in terms of attention span and reduced processing speed [8-15], as well as reduced social and recreational activities [10] and employment status [16].

Common cognitive and behavioral impairments related to executive function after an mTBI include the following: difficulties with attention, memory, planning, decision-making, emotional control, motivation and impulsivity [17]. Attention is an important factor for executive function and distractibility is suggested to be one of the most troublesome effects after an mTBI [18]. In the clinic, mTBI patients commonly comment that important as well as unimportant information is recognized and that they are easily distracted even when, according to normative data cognitive tests are within normal range. Only a few studies in clinical populations have been reported measuring cognitive function while a distraction is present. The ability to apply and sustain one’s attention in the presence of a distractor in the form of background noise was studied with participants who had suffered an mTBI [18]. The test consisted on an extended version of the 2 and 7 Selective Attention test [19] adding two distractors, a non-relevant distraction involving a background noise from a radio talk show and a relevant distractor involving instructions from a tape recorder on how to calculate a math problem. The processing speed was found to be reduced for mTBI group on the relevant distractor task. Accuracy was maintained for controls and the mTBI subjects. The symptoms of slowed thinking and fatigue were related to processing speed in the non-relevant distractor task and the relevant noise distractor task was related to processing speed and slowness of thinking. A study with a visual reaction time go-no-go task adding a visual distractor with a varied onset time was done. This was used to compare a group who had suffered a TBI with a control group [20]. When the distractor occurred at or shortly after the target a slowing in reaction time was detected; this was significantly greater for the TBI group. Accuracy was not affected. The authors suggest that the distractor caused most interference with response planning and execution as opposed to target detection. From another study, comparison was done between mTBI, a group with major depression and a control group using standard neuropsychological tests in a standard setting and in a setting with visual and auditory distractors [21]. While reading the story during the logical memory test from the Wechsler Memory Scale (WMS), a distraction with a woman reading the news was shown on a laptop screen and, when conducting the subtest Digit Span and Letter-Number-Sequencing from the Wechsler Adult Intelligence Scale (WASI-IV) a distraction with random number of digits was shown on the computer screen. Baseline testing without distraction showed similar results between the groups while a significant deterioration in working memory during distraction setting was found for the mTBI group. The control group remained unchanged. The depressed group improved during the test session on working memory during the distraction setting and reported more emotional distress compared to the mTBI and control groups. The mTBI group reported dizziness, headaches and feeling puzzled and these patients did not report emotional distress as a result of the distraction. The author also concluded that significant change in the distraction condition indicate that the patient is not ready to successfully return to an occupation involving complex attentional demands [21]. In a memory and virtual street task with distractors the group with severe TBI performed less well compared with the controls and was also more affected by distractions while no difference in logical memory (WMS-III) was found between the groups [22].

Only a few studies are reported in clinical populations exploring distraction in relation to mental fatigue. Fatigue and cognitive dysfunction are common among people suffering from Multiple Sclerosis (MS), and when cognitive tests with and without distraction, mimicking background office noise was compared, reduced processing speed was found for MS participants in presence of an auditory distraction [23]. From a study of patients suffering from stress-related exhaustion, increased mental fatigue was reported after a neuropsychological testing with auditory distraction. The control group did not rate any changes in mental fatigue. Compared to the control group, cognitive performance was not affected according to common neuropsychological tests measuring executive function, working memory and complex attention [24].

Attention is commonly categorized into two distinct functions; the goal-driven and voluntary allocation of attention referred to as top-down or endogenous attention, and the stimulus-driven attention referred to as bottom-up or exogenous attention, being driven by external events in the environment [25]. Normally, by filtering out less relevant information people allows to respond quickly and to achieve behavioral goals more efficiently. Processes mediating bottom-up and top-down attention has been argued, and a frontoparietal network is suggested being essential in both types of attentional processes, based on studies in nonhuman primates [26]. Tommasi et al. [27] used a computerized test measuring attentional capture and goal-driven attention with a salient distractor, with the intention to compare top-down and bottom-up attention. They reported increased distractibility for the Parkinson’s group compared to the controls, with the Parkinson group having a slower reaction time and more omissions when the distractor was present and having an increase in time of attentional capture and a delay in target selection in the absence of any salient distractor. They suggested that their result reflect impaired top-down attention compared with controls. They did not include fatigue in their study, but fatigue is common among patients suffering from Parkinson´s disease [28]. Liu et al. evaluated mental fatigue associated with mTBI using a psychomotor vigilance test combined with arterial spin labeling fMRI (functional Magnetic Resonance Imaging) [29] and suggested that mental fatigue was associated with both weakened top-down and bottom-up attention.

The present study was based on the work performed by Tommasi et al. [27] and the objective was to investigate distraction and the influence of top-down and bottom-up attention among people who suffer from mental fatigue after mTBI.

Materials and Methods


The clinical group consisted of 30 people who had sustained mTBI and were suffering from mental fatigue at least 6 months after the mTBI. Their injury was evaluated on the basis of a personal interview and they were diagnosed with mTBI according to the definition proposed by The WHO Collaborating Centre for Neurotrauma Task Force on Mild Traumatic Brain Injury [30], having a sum score above the cut-off score on the Mental Fatigue Scale (MFS, cut-off 10.5) [31]. The patients were aged 20-65 years and were not suffering from any other psychiatric or neurological disorders. Eight had been receiving stimulant medication for approximately 5-6 years but had not taken methylphenidate for four weeks prior to inclusion in this study. Their cognitive test results and rating on MFS had returned to baseline after four weeks without methylphenidate [32]. All mTBI participants had recovered well and were independent in their daily lives, with the exception of their prolonged mental fatigue. The clinical group was selected from a rehabilitation unit and a pain clinic and from an announcement in a Facebook group for mental fatigue as it was not possible to recruit enough patients from the clinics. No specific concussion nor mTBI clinic was present. Thirty healthy controls, also aged 20-65, who neither suffered from mental fatigue (below 10.5 points on MFS), nor from any psychiatric or neurological disorders were recruited at the request of the general community. The study was approved by the regional Ethical Review Board in Gothenburg. The participants gave their informed consent. All received a cinema ticket to thank for their participation.

Self-assessment scales

The Mental Fatigue Scale (MFS) is a multidimensional questionnaire comprising 15 questions. Each question included examples of common activities and was then related to four exemplified alternatives. Higher scores reflected a more severe symptom. The questions included in the scale were found to have an adequate internal consistency with a Cronbach´s alpha of 0.944S [33]. MFS has a cutoff score at 10.5 [34]. MFS has been evaluated for TBI and stroke subjects and was found to be invariant in patients aged 18- 65 years; it did not vary with time since injury, gender and education [10,34]. An evaluation of MFS demonstrated that processing speed was a significant cognitive predictor for rating on MFS [10,34].

The Comprehensive Psychopathological Rating Scale (CPRS) was used to assess depression and anxiety [35,36]. The CPRS depression scale is identical to the Montgomery Åsberg Depression Rating Scale (MADRS) except that the rating is doubled up in the MADRS [37]. Mild depression (according to CPRS rating) has been associated with a rating ranging between 6.6 and 9.5 for mild; moderate between 10- 17; and severe ≥17.5 [38].

The MFS and CPRS have a similar construction with four exemplified alternatives for each question, making it easy to compare the ratings from the two scales. Four items from the MFS and CPRS are overlapping and are the same. Concentration difficulties, lack of initiative and decreased sleep are all included in MFS and CPRS depression; irritability is included in MFS and CPRS anxiety (the separate items are shown in Figure 2).

Test procedure

A computerized test was used based on the test described by Tommasi et al. [27]. Their test procedure was adapted for participants with Parkinson’s disease; their objective was to study attention and distraction/stimulus. This is a test with an attentional capture task/ distractor (AC). AC is defined as an involuntary directed attention towards a target stimulus/distractor [39]. The computerized test was adapted to run on PC [27] by a professional computer programmer (Figure 1).