Consequences of mild traumatic brain injury on information processing assessed with attention and short-term memory tasks

In this investigation, we explored the impact of mild traumatic brain injury (mTBI) upon short term or working memory and attention. The performance of 37 individuals with mTBI was compared with that of 53 age, sex and education-matched controls. All participants were staff members or individuals seeking medical care at a University hospital serving a large metropolitan area. A battery of computerized tests measured sustained visual attention, short-term memory (STM), simple reaction time, and decision time. Individuals with mTBI showed a performance deficit at sustained visual attention, STM scanning and a trend towards slowing in choice decision making. These observed changes in the cognitive performance of mTBI individuals are hypothesized to be a consequence of impaired central information processing. Our results suggest that mTBI can elicit meaningful cognitive deficits for several months post-injury. Additionally, we believe that the tasks employed in the current investigation demonstrate their utility for understanding cognitive deficits in mTBI individuals.     

Physiological dysfunction of the dorsolateral prefrontal cortex in schizophrenia revisited

Evidence implicates subtle neuronal pathology of the prefrontal cortex (PFC) in schizophrenia, but how this pathology is reflected in physiological neuroimaging experiments remains controversial. We investigated PFC function in schizophrenia using functional magnetic resonance imaging (fMRI) and a parametric version of the n-back working memory (WM) task. In a group of patients who performed relatively well on this task, there were three fundamental deviations from the 'healthy' pattern of PFC fMRI activation to varying WM difficulty. The first characteristic was a greater magnitude of PFC fMRI activation in the context of slightly impaired WM performance (i.e. physiological inefficiency). The second was that the significant correlations between behavioral WM performance and dorsal PFC fMRI activation were in opposite directions in the two groups. Third, the magnitude of the abnormal dorsal PFC fMRI response was predicted by an assay of N-acetylaspartate concentrations (NAA) in dorsal PFC, a measure of neuronal pathology obtained using proton magnetic resonance spectroscopy. Patients had significantly lower dorsal PFC NAA than controls and dorsal PFC NAA inversely predicted the fMRI response in dorsal PFC (areas 9, 46) to varying WM difficulty - supporting the assumption that abnormal PFC responses arose from abnormal PFC neurons. These data suggest that under certain conditions the physiological ramifications of dorsal PFC neuronal pathology in schizophrenia includes exaggerated and inefficient cortical activity, especially of dorsal PFC.     

Transmitters involved in central processing of nociceptive information

Distribution studies suggest that substance P is a transmitter released by nociceptive primary afferent fibres. Acceptance of this role, however needs more electro-physiological comparisons of the effects of substance P and the transmitter released by primary afferents on the membrane properties of dorsal horn neurones. The transmission of impulses from nociceptive afferents to supraspinal areas is subject to inhibition of both segmental and supraspinal origin. Segmental inhibition probably involves glycine and gamma-aminobutyric acid as transmitters. Of supraspinal inhibitions investigated in the cat none have been shown to involve amino acids, enkephalins or 5-hydroxytryptamine but there is evidence to suggest a role for noradrenaline.     

Speed of information processing in traumatic brain injury: modality-specific factors

OBJECTIVE: To assess speed of information processing by two serial addition tests (one visual, one auditory) in individuals with moderate-to-severe traumatic brain injuries (TBIs) and in a healthy, normal control group (NC). The tasks were designed to equate and control for accuracy of performance across the TBI and NC groups, thus allowing for quantification of information processing speed. DESIGN: Performance across groups and tasks were compared using 2 x 2 repeated measure analyses of variance (ANOVAs). In addition, each individual's processing speed was used to adjust rate of stimulus presentation on a subsequent "rehabilitation" trial to determine further whether this adjustment equated accuracy of performance. SETTING: Rehabilitation hospital. PATIENTS: 22 outpatients with moderate-to-severe TBI (6 women, 16 men; mean age = 34.6 years; duration of loss of consciousness = 22.6 days) and 20 age- and education-matched healthy controls. RESULTS: Processing speed was slower in TBI subjects, relative to controls and was significantly related to measures of executive functioning for those with TBI. Relative to controls, speed of processing in the TBI group was disproportionately slower when information was presented in the auditory, relative to the visual, modality. CONCLUSIONS: Speed of information processing is a major impairment in those with TBI when unconfounded by performance accuracy. The modality-specific impairment observed in the TBI group may, in part, be due to a greater within-modality interference effect created by the auditory version of the task. By manipulating information at a pace customized for an individual through compensatory strategies and environmental modifications, information-processing performance of TBI participants can be enhanced significantly.     

Changes in speed of information processing in the brain following tendon repair

The objective of this study was to measure the "preparation time" that is the speed of information processing in the brain, and discuss the relevance of this parameter in the restoration of hand function following flexor tendon repair. The preparation time of 48 healthy adult participants was measured twice at a 6-week interval and compared with that of 12 patients after flexor tendon repair. There was no difference between the left and right hands of the healthy participants. The correlation between repeated measurements was high, although healthy participants performed 2.6% faster 6 weeks after the first measurement. After 6 weeks of immobilisation, patients showed a significant deterioration with respect to the speed of information processing by the brain on both the injured and uninjured sides compared with healthy participants, who had improved between the first and the second measurements. The results indicate that a period of lack of normal use of the hand leads to a change in cerebral control of hand movements.     

Improved prediction of success in surgical clerkship through measures of information processing

A new system for predicting success of surgical student performance has been developed. A test of surgical knowledge, with questions given in the form of analogies, was administered to 16 students in their fourth week of clerkship. While solving test items, students' eye movements and fixations were tracked. By analysis of the recordings, eight scores of information-processing capabilities were derived. The processing scores and conventional predictors of medical school clinical performance were analyzed to determine their power to predict success, defined by ratings given on a 1 to 10 scale by 21 faculty members based on three tests of cognitive knowledge, two performance-based examinations, and faculty reports. The ratings were reliable (generalizability coefficient = 0.72; p less than 0.001). Stepwise regression analysis of all variables selected one MCAT score (science problems) and two information-processing scores to the statistical model that maximally predicted success. Regression coefficient for the science problem subset of the MCAT was 0.42. This was augmented to R2 = 0.77 when information processing variables were included. The increment was significant, F (2, 11) = 9.25; p less than 0.01. A newly developed test, coupled with techniques that made possible the derivation of components of information processing, nearly doubled the power of conventional tests to predict success in surgical clerkship.     

The effects of post-traumatic amnesia on information processing following mild traumatic brain injury

PRIMARY OBJECTIVE: The aim of this study was to determine whether a single measurement of level of PTA could distinguish patients more severely injured from those less so, by investigating the effect of PTA on psychometric test performance. METHODS AND PROCEDURES: Ninety patients with mTBI completed a word recall test, a spoken version of the Speed of Comprehension test and the Digit Symbol Substitution Test (Digit Symbol), within 24 hours of injury. These patients were divided into two groups, based on the presence (n=42) or absence (n=48) of PTA at the time of testing. PTA was measured with an eight-item orientation scale. MAIN OUTCOMES AND RESULTS: An independent groups design showed that patients with mTBI in PTA recalled fewer words after two presentations and after a delay and completed fewer symbols in 90 seconds on Digit Symbol than patients with mTBI not in PTA. Discriminant function analysis was applied to explore whether classifying severity of injury in terms of number of orientation questions answered would be useful. CONCLUSIONS: These results indicate that for individuals with mTBI in PTA, speed of information processing and verbal memory are impaired. A single brief administration of orientation questions may be sufficient to provide an index of severity of mTBI within the first 24 hours.     

Filling-in in schizophrenia: a high-density electrical mapping and source-analysis investigation of illusory contour processing

Evidence is accumulating that patients with schizophrenia exhibit relatively severe deficits in early visual sensory processing within the dorsal stream, while processing within the ventral stream appears to be relatively more intact. Here, illusory contour (IC) processing was investigated in a cohort of schizophrenia patients and age-matched healthy controls using high-density visual evoked potentials (VEPs), spatiotemporal topographic analyses and the Local Auto-Regressive Average distributed linear inverse source estimation. IC processing was assessed because it is now known to be an excellent metric of early processing within regions of the ventral visual stream. Results in the present study show that IC processing (106-194 ms) is spared in patients with schizophrenia, providing strong evidence that early ventral stream processing is essentially normal. This is so despite equally strong evidence that early dorsal stream processing is severely impaired in this population, as indexed by a robust decrement in amplitude of the P1 component in patients and a large topographic difference between groups for this component (54-104 ms). Source analysis confirmed that the flow of activity into the dorsal stream was substantially decreased in patients. As such, these results suggest that some aspects of early ventral processing are not entirely reliant on intact inputs from the dorsal stream. Lastly, we show that later phases of visual processing (240-400 ms) also rely on the activity of different brain networks in controls and patients, with the latter recruiting strong frontal activity perhaps as compensation for impaired ventral stream processing during this period. We interpret the present findings in the context of a two-stage processing model. Under this model, it is suggested that the second stage of ventral stream processing is dependent on the fidelity of inputs from the dorsal visual stream and that impairment of this critical modulatory input may underlie the failure of 'higher-level' ventral stream processes in this population.     

Effects of laparoscopic sleeve gastrectomy on attentional processing of food-related information: Evidence from eye-tracking

BackgroundWeight loss after laparoscopic sleeve gastrectomy (LSG) might be associated partially with changes in reward system functioning and altered appetitive responses to food cues. Food cue processing refers to motivational, affective, and cognitive responses to stimuli that are associated with food. We investigated if food cue processing is altered 6 months after weight loss that is induced by LSG. We expected patients after LSG to show reduced appetitive responses to food cues.MethodsIn an experimental longitudinal exploratory study, 17 severely obese patients (body mass index [BMI]: 48.3±6.5 kg/m²) were investigated presurgery and 6 months postsurgery. We used eye-tracking to assess attentional biases during free viewing of food versus nonfood cues, assessed pleasantness ratings of food cues, and self-reported food craving.ResultsAfter LSG, the mean BMI of patients was 36.4±6.0 kg/m², and the percentage of excess weight loss (%EWL) was 46.6%±14.0%. Six months after LSG, patients showed an attentional bias toward nonfood cues compared with presurgery, reported lower food craving, and rated presented food stimuli as less pleasant.ConclusionEvidence of altered food cue processing was found in patients after LSG, which may be interpreted as reduced food reward associated with increased cognitive control. Surgery-induced physiologic, cognitive-motivational, and behavioral changes may lead to a desensitization of the reward system and enhanced cognitive control.     

Distinct and convergent visual processing of high and low spatial frequency information in faces

We tested for differential brain response to distinct spatialfrequency (SF) components in faces. During a functional magneticresonance imaging experiment, participants were presented with"hybrid" faces containing superimposed low and high SF informationfrom different identities. We used a repetition paradigm wherefaces at either SF range were independently repeated or changedacross consecutive trials. In addition, we manipulated whichSF band was attended. Our results suggest that repetition andattention affected partly overlapping occipitotemporal regionsbut did not interact. Changes of high SF faces increased responsesof the right inferior occipital gyrus (IOG) and left inferiortemporal gyrus (ITG), with the latter response being also modulatedadditively by attention. In contrast, the bilateral middle occipitalgyrus (MOG) responded to repetition and attention manipulationsof low SF. A common effect of high and low SF repetition wasobserved in the right fusiform gyrus (FFG). Follow-up connectivityanalyses suggested direct influence of the MOG (low SF), IOG,and ITG (high SF) on the FFG responses. Our results reveal thatdifferent regions within occipitotemporal cortex extract distinctvisual cues at different SF ranges in faces and that the outputsfrom these separate processes project forward to the right FFG,where the different visual cues may converge.     

Spinal cord trauma activates processing of xbp1 mRNA indicative of endoplasmic reticulum dysfunction

The contribution of the various subcellular compartments in the induction of cell injury triggered by spinal cord trauma has not been clearly elucidated yet. In the present study, we investigated changes in mRNA levels of processed xbp1, ho-1, and hsp70 induced in mice by hemisection or contusion of the spinal cord. The expression of these genes is upregulated under conditions associated with endoplasmic reticulum (ER; xbp1, ho-1) dysfunction or impairment of cytoplasmic function (hsp70) respectively. When the functioning of the ER or the cytoplasm is impaired, unfolded proteins accumulate in these compartments. This is the warning signal for activation of the unfolded protein response (ER) and heat-shock response (cytoplasm) respectively. Spinal cord trauma activated the expression of these genes starting at 3 h and peaking at 6 h of recovery (processed xbp1, 12-fold and fivefold increase; ho-1, fourfold and eightfold increase; hsp70, fourfold, no increase, after contusion and hemisection, respectively). After 6 h of recovery, the rise in hsp70 mRNA levels was confined to the traumatized segment (fourfold), whereas a significant increase in processed xbp1 and ho-1 mRNA levels was also observed in the adjacent segments. This suggests a spread of the pathological process from the site of the primary impact into the surrounding tissue. After induction of spinal cord trauma processed xbp1 mRNA levels rose in a delayed fashion. This implies that the pathological process that causes impairment of ER functioning, starts with a delay of a few hours after induction of trauma and may therefore be amenable to therapeutic intervention.     

Consequences of haemostasis disorders on anaesthestic management

New molecular markers of coagulation and fibrinolysis activation have been developed and used to identify patient subgroups that frequently develop increased procoagulant turnover and, hence, disseminated intravascular coagulation and organ dysfunction. The idea of inhibiting the coagulation hyperactivation by the administration of antithrombin has led to experimental findings that pinpoint an anti-inflammatory action of antithrombin. Preliminary clinical trials of high-dose antithrombin administration in sepsis are promising. Point-of-care coagulation testing remains controversial since a variety of perioperative therapeutic regimens such as aprotinin administration obviously do not require 'on-line' coagulation monitoring.     

Attentional control and slowness of information processing after severe traumatic brain injury

Attention is a basic cognitive function and a prerequisite for other cognitive processes and is frequently impaired after traumatic brain injury. In the present study, 29 severe traumatic brain injury patients and 30 control subjects completed a battery of three neuropsychological tests of attention (WCST, TMT, Stroop). The aim was to clarify the attentional mechanisms underlying tests performance and to explore the types of attentional impairment after severe traumatic brain injury. Significant differences were found between the control and clinical groups in almost all measures. However, some of these differences disappeared when the speed of information processing was controlled using covariance analysis. In addition, a factor analysis revealed a four-factor solution explaining 89.6% of the variance in the data, i.e. cognitive flexibility, speed of processing, interference and working memory. This result supports the view of at least four different subprocesses of attentional control underlie test performance and allows one to differentiate between high- and low-level processes. The implications for neuropsychological assessment and rehabilitation are discussed.     

Consequences of bilateral cryptorchidism in adults

Bilateral cryptorchidism treatment results are often shadowed by the majority of unilateral cases. We report the long‐term follow‐up results of boys treated for bilateral cryptorchidism during childhood. Patients treated in two main paediatric surgery centres were selected from medical registries and invited for a clinical examination including scrotal ultrasound, salivary testosterone measurement and a semen sample. Thirty‐six men (38.3%) replied to the written invitation, and 21 agreed to be examined. The mean age at orchidopexy was 74 months (range 24–138). Sperm count was 0.42 × 10⁶ (SD ± 0.64 × 10⁶) ml^?1. The correlation between total testicular volume and total sperm count was statistically significant (r = 0.481; P = 0.032). These results show that surgical treatment of bilateral cryptorchidism after the age of 2 years does not prevent infertility. Sperm count and endocrine evaluation advocated after the treatment of bilateral cryptorchidism in all adult patients.