The psychological neuroscience of depression: implications for understanding effects of deep brain stimulation

In this article it is suggested that current psychological theories of depression presuppose that this condition will develop as a result of a vicious circle involving negatively biased communication between systems of emotional stress-/alarm-signaling, executive functions and mood regulation. These systems may from a neuroanatomical point of view be located in the limbic system, the orbitofrontal and lateral prefrontal cortex and the hypothalamus-pituitary-adrenal (HPA-) axis respectively. The theoretical and practical implications of this model for the understanding of pharmacological treatments of depression are briefly discussed and this theory is related to the catecholamine hypothesis of depression. The model is furthermore discussed in relation to deep brain stimulation (DBS) of treatment resistant major depression. Similarities and differences between this perspective and the one advocated by the "homeostatic theory" of depression are discussed. It is concluded that a topographical psychological theory may offer a useful heuristic in thinking about depression and that it offers several testable predictions about treatments of the disorder.     

Modulation of N400 in chronic non-fluent aphasia using low frequency Repetitive Transcranial Magnetic Stimulation (rTMS)

Low frequency Repetitive Transcranial Magnetic Stimulation (rTMS) has previously been applied to language homologues in non-fluent populations of persons with aphasia yielding significant improvements in behavioral language function up to 43 months post stimulation. The present study aimed to investigate the electrophysiological correlates associated with the application of rTMS through measurement of the semantic based N400 Event-related brain potentials (ERP) component. Low frequency (1 Hz) rTMS was applied to the anterior portion of the homologue to Broca’s area (pars triangularis), for 20 min per day for 10 days, using a stereotactic neuronavigational system. Twelve non-fluent persons with aphasia, 2-6 years post stroke were stimulated. Six participants were randomly assigned to receive real stimulation and six participants were randomly assigned to receive a blind sham control condition. ERP measures were recorded at baseline, 1 week and 2 months subsequent to stimulation. The findings demonstrate treatment related changes observed in the stimulation group when compared to the placebo control group at 2 months post stimulation indicating neuromodulation of N400 as a result of rTMS. No treatment related changes were identified in the stimulation group, when compared to the sham group from baseline to 1 week post stimulation. The electrophysiological results represent the capacity of rTMS to modulate neural language networks and measures of lexical-semantic function in participants with non-fluent aphasia and suggest that time may be an important factor in brain reorganization subsequent to rTMS.     

Musicians and tone-language speakers share enhanced brainstem encoding but not perceptual benefits for musical pitch

Behavioral and neurophysiological transfer effects from music experience to language processing are well-established but it is currently unclear whether or not linguistic expertise (e.g., speaking a tone language) benefits music-related processing and its perception. Here, we compare brainstem responses of English-speaking musicians/non-musicians and native speakers of Mandarin Chinese elicited by tuned and detuned musical chords, to determine if enhancements in subcortical processing translate to improvements in the perceptual discrimination of musical pitch. Relative to non-musicians, both musicians and Chinese had stronger brainstem representation of the defining pitches of musical sequences. In contrast, two behavioral pitch discrimination tasks revealed that neither Chinese nor non-musicians were able to discriminate subtle changes in musical pitch with the same accuracy as musicians. Pooled across all listeners, brainstem magnitudes predicted behavioral pitch discrimination performance but considering each group individually, only musicians showed connections between neural and behavioral measures. No brain-behavior correlations were found for tone language speakers or non-musicians. These findings point to a dissociation between subcortical neurophysiological processing and behavioral measures of pitch perception in Chinese listeners. We infer that sensory-level enhancement of musical pitch information yields cognitive-level perceptual benefits only when that information is behaviorally relevant to the listener.     

Long‐Term Outcomes of Traumatic Brain Injury in Early Childhood

Mild traumatic brain injury (mTBI) is a leading cause of injury among children, with approximately 15% of children experiencing a TBI prior to 15 years of age. Acutely, mTBI has been associated with a range of cognitive, physical, emotional and behavioural impairments. However, few studies have examined outcomes beyond five years post injury, long before the developmental process is complete and the full extent of any deficits may manifest. Our group had the unique opportunity to use data from a longitudinal birth cohort of 1265 children (Christchurch Health and Development Study) to examine the long term outcomes of early injury (0–5 years). Information about these children, including mTBI events, had been collected at birth, 4 months and at yearly intervals until age 16, and again at ages 18, 21 and 25 years. We found that even after statistical control for a wide range of child and family confounds, children who had been hospitalized for an mTBI had increased inattention/hyperactivity and conduct as rated by mothers and teachers over ages 7–13 years. Increased rates of psychiatric disorders were over 14–16 years for those injured in the preschool, including symptoms consistent with Attention Deficit/Hyperactivity Disorder (ADHD), Odds Ratio = 4.6, Conduct Disorder (CD), Odds Ratio = 5.6 and Substance Abuse (Odds Ratio = 9.1). Over ages 21–25 ongoing behaviour problems were assessed using self‐reported arrests, violent offenses and property offenses. Compared to non‐injured individuals, mTBI groups were more likely to be arrested, involved in property, and violent offences. We controlled for a wide range of factors and there was still clear evidence of ongoing problems for individuals who had experienced a mTBI compared to their non injured counterparts. These findings provide compelling evidence of long term psychosocial and psychiatric outcomes following mTBI.     

Cerebral perfusion and neuropsychological follow up in mild traumatic brain injury: Acute versus chronic disturbances?

In a subgroup of patients with mild traumatic brain injury (TBI) residual symptoms, interfering with outcome and return to work, are found. With neuropsychological assessment cognitive deficits can be demonstrated although the pathological underpinnings of these cognitive deficits are not fully understood. As the admission computed tomography (CT) often is normal, perfusion CT imaging may be a useful indicator of brain dysfunction in the acute phase after injury in these patients.In the present study, directly after admission perfusion CT imaging was performed in mild TBI patients with follow-up neuropsychological assessment in those with complaints and a normal non-contrast CT. Neuropsychological tests comprised the 15 Words test Immediate Recall, Trailmaking test part B, Zoo Map test and the FEEST, which were dichotomized into normal and abnormal. Perfusion CT results of patients with normal neuropsychological test scores were compared to those with abnormal test scores.In total eighteen patients were included. Those with an abnormal score on the Zoo Map test had a significant lower CBV in the right frontal and the bilateral parieto-temporal white matter. Patients with an abnormal score on the FEEST had a significant higher MTT in the bilateral frontal white matter and a significant decreased CBF in the left parieto-temporal grey matter. No significant relation between the perfusion CT parameters and the 15 Words test and the Trailmaking test part B was present.In conclusion, impairments in executive functioning and emotion perception assessed with neuropsychological tests during follow up were related to differences in cerebral perfusion at admission in mild TBI. The pathophysiological concept of these findings is discussed.     

Predictive validity of the Westmead Post-Traumatic Amnesia Scale for functional outcomes in school-aged children who sustained traumatic brain injury

The Westmead Post-Traumatic Amnesia Scale (WPTAS) is routinely used for the assessment of post-traumatic amnesia (PTA) in children who sustained traumatic brain injury (TBI). Yet, the WPTAS' predictive validity for functional outcomes is largely unknown. We aimed to determine whether PTA duration measured by the WPTAS (i) differentially predicts functional outcomes and (ii) contributes to predictions of outcomes beyond the Glasgow Coma Scale (GCS) in children who sustained TBI. Participants were children and adolescents with moderate-to-severe TBI (n = 55) aged 8–15 years. PTA duration was assessed with the WPTAS. Outcomes at the first outpatient follow-up were scored on the Kings Outcome Scale for Childhood Head Injury (KOSCHI) and the TBI Outcome Domain Scale-Extended (ODS-E). Longer PTA and lower GCS were both significantly correlated with worse (i) global outcomes: presence of disability on the KOSCHI and lower score on the ODS-E and (ii) select specific outcomes on the ODS-E: mobility, mood and cognition. PTA duration predicted cognitive outcome on the ODS-E independently, beyond GCS. Together, PTA duration and GCS, predicted the global KOSCHI outcome, as well as the ODS-E mobility and mood outcomes. Neither GCS nor PTA duration correlated with the ODS-E communication, impulsivity/disinhibition, headache, fatigue, sensory impairments or somatic complaints outcomes. PTA duration measured by the WPTAS is a significant unique predictor of functional cognitive outcomes in children who sustained moderate-to-severe TBI, and in combination with the GCS, a significant predictor of global, and several specific functional outcomes.     

Cerebral blood flow in 5‐ to 8‐month‐olds: Regional tissue maturity is associated with infant affect

Infancy is marked by rapid neural and emotional development. The relation between brain function and emotion in infancy, however, is not well understood. Methods for measuring brain function predominantly rely on the BOLD signal; however, interpretation of the BOLD signal in infancy is challenging because the neuronal‐hemodynamic relation is immature. Regional cerebral blood flow (rCBF) provides a context for the infant BOLD signal and can yield insight into the developmental maturity of brain regions that may support affective behaviors. This study aims to elucidate the relations among rCBF, age, and emotion in infancy. One hundred and seven mothers reported their infants' (infant age M ± SD = 6.14 ± 0.51 months) temperament. A subsample of infants completed MRI scans, 38 of whom produced usable perfusion MRI during natural sleep to quantify rCBF. Mother‐infant dyads completed the repeated Still‐Face Paradigm, from which infant affect reactivity and recovery to stress were quantified. We tested associations of infant age at scan, temperament factor scores, and observed affect reactivity and recovery with voxel‐wise rCBF. Infant age was positively associated with CBF in nearly all voxels, with peaks located in sensory cortices and the ventral prefrontal cortex, supporting the formulation that rCBF is an indicator of tissue maturity. Temperamental Negative Affect and recovery of positive affect following a stressor were positively associated with rCBF in several cortical and subcortical limbic regions, including the orbitofrontal cortex and inferior frontal gyrus. This finding yields insight into the nature of affective neurodevelopment during infancy. Specifically, infants with relatively increased prefrontal cortex maturity may evidence a disposition toward greater negative affect and negative reactivity in their daily lives yet show better recovery of positive affect following a social stressor.