Movement preparation and execution: differential functional activation patterns after traumatic brain injury.

Years following the insult, patients with traumatic brain injury often experience persistent motor control problems, including bimanual coordination deficits. Previous studies revealed that such deficits are related to brain structural white and grey matter abnormalities. Here, we assessed, for the first time, cerebral functional activation patterns during bimanual movement preparation and performance in patients with traumatic brain injury, using functional magnetic resonance imaging. Eighteen patients with moderate-to-severe traumatic brain injury (10 females; aged 26.3 years, standard deviation = 5.2; age range: 18.4-34.6 years) and 26 healthy young adults (15 females; aged 23.6 years, standard deviation = 3.8; age range: 19.5-33 years) performed a complex bimanual tracking task, divided into a preparation (2 s) and execution (9 s) phase, and executed either in the presence or absence of augmented visual feedback. Performance on the bimanual tracking task, expressed as the average target error, was impaired for patients as compared to controls (P < 0.001) and for trials in the absence as compared to the presence of augmented visual feedback (P < 0.001). At the cerebral level, movement preparation was characterized by reduced neural activation in the patient group relative to the control group in frontal (bilateral superior frontal gyrus, right dorsolateral prefrontal cortex), parietal (left inferior parietal lobe) and occipital (right striate and extrastriate visual cortex) areas (P's < 0.05). During the execution phase, however, the opposite pattern emerged, i.e. traumatic brain injury patients showed enhanced activations compared with controls in frontal (left dorsolateral prefrontal cortex, left lateral anterior prefrontal cortex, and left orbitofrontal cortex), parietal (bilateral inferior parietal lobe, bilateral superior parietal lobe, right precuneus, right primary somatosensory cortex), occipital (right striate and extrastriate visual cortices), and subcortical (left cerebellum crus II) areas (P's < 0.05). Moreover, a significant interaction effect between Feedback Condition and Group in the primary motor area (bilaterally) (P < 0.001), the cerebellum (left) (P < 0.001) and caudate (left) (P < 0.05), revealed that controls showed less overlap of activation patterns accompanying the two feedback conditions than patients with traumatic brain injury (i.e. decreased neural differentiation). In sum, our findings point towards poorer predictive control in traumatic brain injury patients in comparison to controls. Moreover, irrespective of the feedback condition, overactivations were observed in traumatically brain injured patients during movement execution, pointing to more controlled processing of motor task performance.

Cognitive outcome after surgical clipping versus endovascular coiling in patients with subarachnoid hemorrhage due to ruptured anterior communicating artery aneurysm.

Ruptured anterior communicating artery aneurysms are commonly associated with deficits in memory and executive functions. However, little studies are available on the effect of surgical clipping (SC) and endovascular coiling (EC) on cognitive functioning. This study evaluates cognitive functioning in 35 patients with subarachnoid hemorrhage after ruptured anterior communicating artery aneurysm (ACoA) compared to 20 healthy controls (HC) and assesses the effect of SC (n = 19) compared to EC (n = 16) on cognitive performances. All participants were investigated with an extensive neuropsychological test battery assessing attention, memory and visuospatial and executive functions. The strength of this study is an in-depth investigation of several cognitive domains together and several memory functions together within the auditory-verbal and visuospatial memory domain for unrelated and related information. The ACoA group was significantly more deficient in attention, auditory-verbal and visuospatial memory and executive functions compared to HCs. No significant differences were found between both groups concerning visuospatial functions. Within the patient group, the SC group, as compared to the EC group, showed a significantly worse performance for auditory-verbal and visuospatial memory. No significant differences could be detected between both groups with regard to attention and visuospatial and executive functions. In conclusion, this study provides evidence for the advantage of EC in ACoA patients over SC in terms of cognitive outcome.

Persistent cognitive deficits after whiplash injury: a comparative study with mild traumatic brain injury patients and healthy volunteers.

In this study, we evaluated persistent cognitive deficits in whiplash injury (WI) patients and compared these to cognitive functioning in mild traumatic brain injury (MTBI) patients and healthy controls (HC). Sixty-one patients suffering from a WI were compared with 57 patients suffering from a MTBI and with 30 HC. They were examined with an extensive neuropsychological test battery assessing attention, memory, and visuospatial and executive functions. In both patient groups, participants showed persistent cognitive symptoms (more than 6 months post-injury). The two patient groups did not differ significantly with regard to measurements of attention, memory, and visuospatial and executive functions. The WI group, as compared to the HC group, was found to be significantly more deficient in speed of performance during sustained and divided attention, focused attention, alternating attention, the storage of new auditory-verbal unrelated information into memory, the long-term delayed recall of stored auditory-verbal related information from memory, abstract reasoning and accuracy of performance during planning and problem solving. No differences could be found between both groups concerning speed of information processing, visuospatial abilities and verbal fluency.

Proactive Response Inhibition and Subcortical Gray Matter Integrity in Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI) has been associated with impairments in inhibiting prepotent motor responses triggered by infrequent external signals (ie, reactive inhibition). It is unclear whether proactive preparation to inhibit upcoming responses is also affected (ie, proactive inhibition). Successful inhibition relies on frontosubcortical interactions; therefore, impairments might be linked with gray matter atrophy in subcortical structures. OBJECTIVE: We investigated reactive and proactive inhibition in TBI and control groups, and their relationship with subcortical gray matter. METHODS: Participants performed a response inhibition task in which the probability of stopping was manipulated. Reactive inhibition was measured as the stop-signal reaction time (SSRT) when the probability of stopping was low. Proactive inhibition was measured as the change in SSRT and in go response time with increasing probability of stopping. Subcortical gray matter structures were automatically segmented with FSL-FIRST. Group differences in subregional volume and associations with reactive and proactive inhibition efficiency were investigated using shape analysis. RESULTS: Reactive inhibition was impaired in TBI, as indicated by longer SSRTs. Moreover, the degree of atrophy in subregions of subcortical structures was predictive for SSRT in TBI. In contrast, proactive inhibition was not affected because both groups showed no response time slowing as a function of stopping probability. Proactive inhibition efficiency could be predicted by local volume in the anterior left putamen, bilateral pallidum, and right thalamus in controls but not in TBI. CONCLUSIONS: Our results reveal that proactive inhibition seems unaffected in TBI and that volume of subregions of subcortical nuclei is predictive for response inhibition proficiency and of clinical relevance in TBI.

Social attributions in patients with ventromedial prefrontal hypoperfusion.

Neuroimaging studies have demonstrated that the medial prefrontal cortex is involved in attributions on enduring and abstract trait characteristics of persons, but not in causal attributions of temporary here-and-now events. Moreover, the neural representation of trait information is thought to be located in the ventral part of the medial prefrontal cortex (vmPFC). In order to verify this latter finding, this study compared the performance of 8 patients with hypoperfusion of the vmPFC, 10 with hypoperfusion excluding the vmPFC and 15 healthy controls on trait and causal attribution questionnaires consisting of several events presented in brief written scenarios. We also investigated whether vmPFC hypoperfusion influenced the experienced intensity of the negative or positive valence of the events. Our results showed that patients with ventral hypoperfusion performed significantly worse on trait attributions in comparison with the non-vmPFC group and healthy controls. All groups performed equally well on causal attributions. These findings support previous research suggesting that the vmPFC is critically involved in enduring trait attribution, but not in temporary causal attribution. Considering the emotional experience of valence, the findings showed more intense valence ratings for negative events and persons. This confirms the role of the vmPFC in the modulation and regulation of negative emotions.

Subcortical Volume Loss in the Thalamus, Putamen, and Pallidum, Induced by Traumatic Brain Injury, Is Associated With Motor Performance Deficits.

BACKGROUND: Traumatic brain injury (TBI) has been associated with altered microstructural organization of white matter (WM) and reduced gray matter (GM). Although disrupted WM organization has been linked to poorer motor performance, the predictive value of GM atrophy for motor impairments in TBI remains unclear. OBJECTIVE: Here, we investigated TBI-induced GM volumetric abnormalities and uniquely examined their relationship with bimanual motor impairments. METHODS: 22 moderate to severe TBI patients (mean age = 25.9 years, standard deviation [SD] = 4.9 years; time since injury = 4.7 years, SD = 3.7 years) and 27 age- and gender-matched controls (mean age = 23.4 years; SD = 3.8 years) completed bimanual tasks and a structural magnetic resonance imaging scan. Cortical and subcortical GM volumes were extracted and compared between groups using FreeSurfer. The association between bimanual performance and GM volumetric measures was investigated using partial correlations. RESULTS: Relative to controls, patients performed significantly poorer on the bimanual tasks and demonstrated significantly smaller total GM as well as overall and regional subcortical GM. However, the groups did not show significant differences in regional cortical GM volume. The majority of the results remained significant even after excluding TBI patients with focal lesions, suggesting that TBI-induced volume reductions were predominantly caused by diffuse injury. Importantly, atrophy of the thalamus, putamen, and pallidum correlated significantly with poorer bimanual performance within the TBI group. CONCLUSIONS: Our results reveal that GM atrophy is associated with motor impairments in TBI, providing new insights into the etiology of motor control impairments following brain trauma.

Impaired facial emotion recognition in patients with ventromedial prefrontal hypoperfusion.

Empathy refers to our ability to recognize and share emotions by another human being. Impairment may underlie many of the emotional deficits commonly associated with a range of neuropsychiatric and neurological conditions. The prefrontal cortex (PFC) has long been implicated in these processes, but the specific contribution of subregions of the PFC remain unclear. Studies regarding the role of subregions of the prefrontal cortex such as the ventromedial prefrontal cortex (vmPFC)-in facial emotion recognition have yielded inconsistent results. The present study aimed to investigate the capacity to recognize nonverbal emotional facial expressions in a group of patients with the following: (a) perfusion deficits in the vmPFC (vmPFC group; N = 13), (b) hypoperfusions sparing the vmPFC (nonvmPFC group; N = 12), and in (c) a control group of healthy volunteers (control group; N = 17). Regions of hypoperfusion were identified by means of Single Photon Emission Computed Tomography (SPECT). Participants were asked to recognize facial expressions of the 7 basic emotions (happiness, fear, surprise, anger, disgust, sadness, or neutral). Detection of facial expressions of fear, disgust, and surprise was affected after functional disruption of the vmPFC. The present study confirms the role of the vmPFC in recognizing emotional facial expressions.