Effects of childhood trauma in psychopathy and response inhibition.

Childhood trauma is linked to impairments in executive function and working memory, thought to underly psychological disorders including depression and posttraumatic stress disorder. Research demonstrates that childhood trauma can partially mediate posttraumatic stress disorder in those with executive function deficits. Despite a link with executive function deficit, psychopathy as a consequence of trauma is yet to be studied in this context. The present study investigates the possibility of a relationship between childhood trauma, psychopathic traits, and response inhibition. Eighty participants were tasked to completed the Childhood Traumatic Events Scale (Pennebaker & Susman, 2013), Levenson's Self-Report Psychopathy Scale (Levenson et al., 1995), and Flanker task of response inhibition (Eriksen & Eriksen, 1974). Scores of trauma exposure, psychopathic traits, and reaction times in the Flanker task were measured. Regression analysis revealed no significance for trauma exposure in predicting psychopathic traits (p = .201) and response inhibition (p = .183), indicating that childhood trauma does not strongly predict susceptibility to psychopathic traits or response inhibition deficits. These findings form an important basis on which to build a further understanding of the consequences of childhood trauma exposure, specifically in terms of understanding how specific cognitive functions may be influenced and providing a clearer understanding of how psychopathic traits develop.

Low-Frequency Repetitive Transcranial Magnetic Stimulation to Right Parietal Cortex Disrupts Perception of Briefly Presented Stimuli.

Right parietal cortex has recently been linked to the temporal resolution of attention. We therefore sought to investigate whether disruption to right parietal cortex would affect attention to visual stimuli presented for brief durations. Participants performed a visual discrimination task before and after 10 minutes repetitive transcranial magnetic stimulation (1 Hz) to right or central parietal cortex as well as 20 minutes after the second block of trials. Participants reported the spatial frequency of a masked Gabor patch presented for a brief duration of 60, 120, or 240 ms. We calculated error magnitudes by comparing accuracy to a guessing model. We then compared error magnitudes to blocks with no stimulation, producing a measure of baselined performance. Baselined performance was poorer at longer stimulus durations after right parietal than central parietal stimulation, suggesting that right parietal cortex is involved in attention to briefly presented stimuli, particularly in situations where rapid accumulation of visual evidence is needed.

Mapping of fine-scale rat prefrontal cortex connections: Evidence for detailed ordering of inputs and outputs connecting the temporal cortex and sensory-motor regions.

Cerebral cortex structure is crucially important for cortical organization and function. The organization of prefrontal cortex (PFC) is controversial and here we seek to understand it more clearly through the study of fine-scale cortical connections. To determine the ordering of microscale input and output connections in the rat PFC, we injected small volumes (20-30 nl) of anterograde (Fluro-Ruby) and retrograde (Fluoro-Gold) neuroanatomical tracers into PFC. These injections revealed several connected regions of the brain but here we report findings restricted to PFC to temporal cortex and sensory-motor cortex pathways. In agreement with previous studies incorporating larger injection volumes we found that smaller injection volumes revealed a more detailed, fine-scale ordering of both prefrontal inputs and output connections to the temporal cortex and sensory-motor cortex regions. These findings are also supported by labelling observed from additional tracer injections made into corresponding regions of temporal cortex. The topography observed reflected the ordering seen at a larger level (i.e., with larger injection volumes) but there were some differences in the topography, such as in relation to the direction of ordering. In agreement with earlier work, we found that fine-scale input and output connections were not always aligned with respect to one another. These results provide evidence for topographically arranged inputs and outputs in two distinct PFC pathways, along with evidence for different connectional patterns within the same pathways. Based on theories of functional connectivity, these findings provide evidence for prefrontal cortical regions residing within networks that contribute to different cognitive functions.

Differences in anatomical connections across distinct areas in the rodent prefrontal cortex.

Prefrontal cortex (PFC) network structure is implicated in a number of complex higher-order functions and with a range of neurological disorders. It is therefore vital to our understanding of PFC function to gain an understanding of its underlying anatomical connectivity. Here, we injected Fluoro-Gold and Fluoro-Ruby into the same sites throughout rat PFC. Tracer injections were applied to two coronal levels within the PFC (anterior +4.7 mm to bregma and posterior +3.7 mm to bregma). Within each coronal level, tracers were deposited at sites separated by approximately 1 mm and located parallel to the medial and orbital surface of the cortex. We found that both Fluoro-Gold and Fluoro-Ruby injections produced prominent labelling in temporal and sensory-motor cortex. Fluoro-Gold produced retrograde labelling and Fluoro-Ruby largely produced anterograde labelling. Analysis of the location of these connections within temporal and sensory-motor cortex revealed a consistent topology (as the sequence of injections was followed mediolaterally along the orbital surface of each coronal level). At the anterior coronal level, injections produced a similar topology to that seen in central PFC in earlier studies from our laboratory (i.e. comparing equivalently located injections employing the same tracer), this was particularly prominent within temporal cortex. However, at the posterior coronal level this pattern of connections differed significantly, revealing higher levels of reciprocity, in both temporal cortex and sensory-motor cortex. Our findings indicate changes in the relative organization of connections arising from posterior in comparison to anterior regions of PFC, which may provide a basis to determine how complex processes are organized.

The topology of connections between rat prefrontal and temporal cortices.

Understanding the structural organization of the prefrontal cortex (PFC) is an important step toward determining its functional organization. Here we investigated the organization of PFC using different neuronal tracers. We injected retrograde (Fluoro-Gold, 100 nl) and anterograde [Biotinylated dextran amine (BDA) or Fluoro-Ruby, 100 nl] tracers into sites within PFC subdivisions (prelimbic, ventral orbital, ventrolateral orbital, dorsolateral orbital) along a coronal axis within PFC. At each injection site one injection was made of the anterograde tracer and one injection was made of the retrograde tracer. The projection locations of retrogradely labeled neurons and anterogradely labeled axon terminals were then analyzed in the temporal cortex: area Te, entorhinal and perirhinal cortex. We found evidence for an ordering of both the anterograde (anterior-posterior, dorsal-ventral, and medial-lateral axes: p < 0.001) and retrograde (anterior-posterior, dorsal-ventral, and medial-lateral axes: p < 0.001) connections of PFC. We observed that anterograde and retrograde labeling in ipsilateral temporal cortex (i.e., PFC inputs and outputs) often occurred reciprocally (i.e., the same brain region, such as area 35d in perirhinal cortex, contained anterograde and retrograde labeling). However, often the same specific columnar temporal cortex regions contained only either labeling of retrograde or anterograde tracer, indicating that PFC inputs and outputs are frequently non-matched.

The topology of connections between rat prefrontal, motor and sensory cortices.

The connections of prefrontal cortex (PFC) were investigated in the rat brain to determine the order and location of input and output connections to motor and somatosensory cortex. Retrograde (100 nl Fluoro-Gold) and anterograde (100 nl Biotinylated Dextran Amines, BDA; Fluorescein and Texas Red) neuronanatomical tracers were injected into the subdivisions of the PFC (prelimbic, ventral orbital, ventrolateral orbital, dorsolateral orbital) and their projections studied. We found clear evidence for organized input projections from the motor and somatosensory cortices to the PFC, with distinct areas of motor and cingulate cortex projecting in an ordered arrangement to the subdivisions of PFC. As injection location of retrograde tracer was moved from medial to lateral in PFC, we observed an ordered arrangement of projections occurring in sensory-motor cortex. There was a significant effect of retrograde injection location on the position of labelled cells occurring in sensory-motor cortex (dorsoventral, anterior-posterior and mediolateral axes p < 0.001). The arrangement of output projections from PFC also displayed a significant ordered projection to sensory-motor cortex (dorsoventral p < 0.001, anterior-posterior p = 0.002 and mediolateral axes p < 0.001). Statistical analysis also showed that the locations of input and output labels vary with respect to one another (in the dorsal-ventral and medial-lateral axes, p < 0.001). Taken together, the findings show that regions of PFC display an ordered arrangement of connections with sensory-motor cortex, with clear laminar organization of input connections. These results also show that input and output connections to PFC are not located in exactly the same sites and reveal a circuit between sensory-motor and PFC.