Parietal theta burst TMS does not modulate bistable perception.

The role of the parietal cortex in perceptual awareness and in resolving perceptual ambiguity is unsettled. Early influential transcranial magnetic stimulation studies have revealed differences in conscious perception following parietal stimulation, fuelling the notion that parietal cortex causally contributes to resolving perceptual ambiguity. However, central to this conclusion is the reliability of the method employed. Several prior studies have revealed opposing effects, such as shortening, lengthening, or no effect on multistable perceptual transitions following parietal stimulation. Here we addressed the reliability of continuous theta-burst stimulation (cTBS) on parietal cortex on the perception of bistable stimuli. We conducted three cTBS experiments that were matched to prior experiments in terms of stimuli, stimulation protocol, and target site, and used a higher number of participants. None of our cTBS experiments replicated prior cTBS results. The only experiment using individual functional localizers led to weak effects, while the two others led to null results. Individual variability of motor cortex cTBS did not predict parietal cTBS effects. In view of recent reports of highly variable cTBS effects over motor cortex, our results suggest that cTBS is particularly unreliable in modulating bistable perception when applied over parietal cortex.

Conscious perception of flickering stimuli in binocular rivalry and continuous flash suppression is not affected by tACS-induced SSR modulation.

The content of conscious perception is known to correlate with steady-state responses (SSRs), yet their causal relationship remains unclear. Can we manipulate conscious perception by directly interfering with SSRs through transcranial alternating current stimulation (tACS)? Here, we directly addressed this question in three experiments involving binocular rivalry and continuous flash suppression (CFS). Specifically, while participants (N = 24) viewed either binocular rivalry or tried to detect stimuli masked by CFS, we applied sham or real tACS across parieto-occipital cortex at either the same or a different frequency and phase as an SSR eliciting flicker stimulus. We found that tACS did not differentially affect conscious perception in the forms of predominance, CFS detection accuracy, reaction time, or metacognitive sensitivity, confirmed by Bayesian statistics. We conclude that tACS application at frequencies of stimulus-induced SSRs does not have perceptual effects and that SSRs may be epiphenomenal to conscious perception.

Fractionation of parietal function in bistable perception probed with concurrent TMS-EEG.

When visual input has conflicting interpretations, conscious perception can alternate spontaneously between these possible interpretations. This is called bistable perception. Previous neuroimaging studies have indicated the involvement of two right parietal areas in resolving perceptual ambiguity (ant-SPLr and post-SPLr). Transcranial magnetic stimulation (TMS) studies that selectively interfered with the normal function of these regions suggest that they play opposing roles in this type of perceptual switch. In the present study, we investigated this fractionation of parietal function by use of combined TMS with electroencephalography (EEG). Specifically, while participants viewed either a bistable stimulus, a replay stimulus, or resting-state fixation, we applied single pulse TMS to either location independently while simultaneously recording EEG. Combined with participant's individual structural magnetic resonance imaging (MRI) scans, this dataset allows for complex analyses of the effect of TMS on neural time series data, which may further elucidate the causal role of the parietal cortex in ambiguous perception.

Parietal theta burst TMS: Functional fractionation observed during bistable perception not evident in attention tasks.

When visual input is ambiguous, perception spontaneously alternates between interpretations: bistable perception. Studies have identified two distinct sites near the right intraparietal sulcus where inhibitory transcranial magnetic stimulation (TMS) affects the frequency of occurrence of these alternations, but strikingly with opposite directions of effect for the two sites. Lesion and TMS studies on spatial and sustained attention have also indicated a parcellation of right parietal cortex, into areas serving distinct attentional functions. We used the exact TMS procedure previously employed to affect bistable perception, yet measured its effect on spatial and sustained attention tasks. Although there was a trend for TMS to affect performance, trends were consistently similar for both parietal sites, with no indication of opposite effects. We interpret this as signifying that the previously observed parietal fractionation of function regarding the perception of ambiguous stimuli is not due to TMS-induced modification of spatial or sustained attention.

Expression of the nuclear bile acid receptor/farnesoid X receptor is reduced in human colon carcinoma compared to nonneoplastic mucosa independent from site and may be associated with adverse prognosis.

The nuclear bile acid receptor/farnesoid X receptor (FXR; NR1H4) is involved in bile acid homeostasis, cell proliferation and apoptosis and has been linked to intestinal carcinogenesis in mice. Aim of this study was to analyze FXR expression in human normal intestinal mucosa and colon carcinoma. We achieved systematic mapping of FXR expression of human intestinal mucosa and analysis of 75 human colon carcinomas using FXR immunohistochemistry on formalin-fixed, paraffin-embedded tissue. FXR expression gradually decreased from terminal ileum to the sigmoid colon with strongest expression in the terminal ileum (p < 0.001). FXR expression in carcinomas was reduced compared to peritumoral nonneoplastic mucosa (p < 0.000). Loss of FXR expression was significantly correlated with grading in tumors of the right colon (p = 0.008). FXR expression in tumor and normal tissue showed an inverse correlation with stage. FXR expression in tumor was inversely correlated with clinical outcome. No association was found with patients' age and sex. In nonneoplastic mucosa FXR expression concurred with low expression of Ki-67. In carcinomas, no association was found between FXR expression and Ki-67 and cyclin D1, respectively. Development of colon carcinoma in humans is associated with reduced FXR expression independent of site and may reflect an impaired defense against potentially carcinogenic bile acids along their intestinal gradient. In contrast to normal colon mucosa, FXR expression in carcinomas is not associated with low proliferation. Colon carcinomas with FXR expression seem to be associated with lower stage and a more favourable outcome compared to FXR negative carcinomas.

Myocutaneous flaps and proctocolectomy in severe perianal Crohn's disease--a single stage procedure.

BACKGROUND: Complex perianal wounds can be extremely difficult to treat and primary closure of these defects can be a challenge even for experienced surgeons. So far, myocutaneous flaps for wound closure after removal of malignant tumors are a well-accepted option, but there are only a few reports focusing on the primary closure of the perineal wound after proctocolectomy for Crohn's disease. We describe our experience with wide excision of the diseased perineum using a combined abdominoperineal two-team approach. MATERIALS AND METHODS: We performed proctocolectomy with permanent ileostomy in five patients with longstanding extensive Crohn's disease. All five patients had fistulizing perineal Crohn's disease combined with Crohn's colitis. Each patient received at least one flap for primary wound closure, either a rectus abdominis myocutaneous flap or a gracilis flap. RESULTS: Indication for surgical intervention included anal or bowel stenosis, septic condition, fecal incontinence, or a combination of these features. One patient had a simultaneous adenocarcinoma of the sigmoid colon. Five patients underwent a total of seven flaps. Three months after surgery, complete healing was achieved in all patients; one patient suffered recurrence in the region of his right thigh. Mean follow up was 19.6 months (range-12-43 months). CONCLUSIONS: Myocutaneous flaps are a promising therapeutic option in patients with chronic perianal disease. With the transposition of well-vascularized tissue into the perineal defect, complete healing and control of sepsis can be achieved in the majority of patients.