Temporo-parieto-occipital Junction Research Articles

P01.19.A The temporo-parieto-occipital junction in the non-dominant hemisphere as a challenging hub for glioma surgery: functional and oncological outcomes

Abstract Background The temporo-parieto-occipital junction (TPOJ) in the non-dominant hemisphere is a complex region intersected by multiple white matter bundles (Optic radiations, Inferior-fronto-occipital tract, inferior-longitudinalis-tract, superior-longitudinalis-tract, vertical-occipital-tract, medial-dorsal-longitudinal-tract, parietal-aslant-tract), subserving several high-level neurological functions such as spatial recognition, visual agnosia, visual field, attention and working memory. Few data are available on the optimum brain mapping strategy to be adopted for resecting tumors involving this area. Ideally it should allow surgeon to effectively identify several tracts and safely preserve all functions. Material and Methods We developed a proper protocol to approach this complex area integrating, in awake condition, intraoperative visual test (iVT) to mapping visual field, semantic association test (SRAT) to prevent visual agnosia and preserve working memory, hand manipulation task (hMT) to preserve spatial abilities. We reviewed its efficacy in a series of 38 patients with tumors involving non-dominant TPOJ, looking to functional (neurologic-neuropsychological) and oncological (EOR) outcomes. we perform a lesion symptom map and a disconnectome analysis to evaluate what region predict a decline in neuropsychological function and which tract of white brain matter are correlated in the decline of performance. Results Feasibility was high and all patients were able to perform and complete the protocol, which lasted, on the average11 min cortically and 25 min subcortically. Specificity was >95%. Immediate post-operative deficits were documented in 87.4% of patients, permanent in 3.9% (visual field, visual spatial abilities). Attentive and emotional domains were those mostly affected in the neuropsychological evaluation. Lesion symptom mapping and disconnectomic analysis showed that the postoperative decrease in neuropsychological performance was associated with resection of a cluster of voxels corresponding to the anterior portion of the temporo-parietal junction. The white matter tracts mainly involved were the anterior and posterior segment of the middle longitudinal fasciculus (aMdLF and pMdLF) and the parietal aslant tract (PAT). Conclusion Effective and safe resection of tumors involving non-dominant TPOJ is feasible. The adoption of a specific brain mapping protocol in awake setting is recommended to achieve a full functional preservation and extend tumor resection. Further analysis should be performed to assess the role of this subcortical tracts.

Surface-Based Amplitude of Low-Frequency Fluctuation Alterations in Patients With Tinnitus Before and After Sound Therapy: A Resting-State Functional Magnetic Resonance Imaging Study.

This study aimed to investigate abnormal tinnitus activity by evaluating brain surface-based amplitude of low-frequency fluctuation (ALFF) changes detected by resting-state functional magnetic resonance imaging (RS-fMRI) in patients with idiopathic tinnitus before and after 24 weeks of sound therapy. We hypothesized that sound therapy could gradually return cortical local brain function to a relatively normal range. In this prospective observational study, we recruited thirty-three tinnitus patients who had undergone 24 weeks of sound therapy and 26 matched healthy controls (HCs). For the two groups of subjects, we analyzed the spontaneous neural activity of tinnitus patients by cortical ALFF and detected its correlation with clinical indicators of tinnitus. Patients’ Tinnitus Handicap Inventory (THI) scores were assessed to determine the severity of their tinnitus before and after treatment. Two-way mixed model analysis of variance and Pearson’s correlation analysis were used in the statistical analysis. Student–Newman–Keuls tests were used in the post hoc analysis. Interaction effects between the two groups and between the two scans revealing local neural activity as assessed by ALFF were observed in the bilateral dorsal stream visual cortex (DSVC), bilateral posterior cingulate cortex (PCC), bilateral anterior cingulate and medial prefrontal cortex (ACC and MPC), left temporo-parieto-occipital junction (TPOJ), left orbital and polar frontal cortex (OPFC), left paracentral lobular and mid cingulate cortex (PCL and MCC), right insular and frontal opercular cortex (IFOC), and left early visual cortex (EVC). Importantly, local functional activity in the left TPOJ and right PCC in the patient group was significantly lower than that in the HCs at baseline and was increased to relatively normal levels after treatment. The 24-week sound therapy tinnitus group demonstrated significantly higher ALFF in the left TPOJ and right PCC than in the tinnitus baseline group. Also, compared with the HC baseline group and the 24-week HC group, the 24-week sound therapy tinnitus group demonstrated slightly lower or higher ALFF in the left TPOJ and right PCC, and there were no differences between the 24-week sound therapy tinnitus and HC groups. Decreased THI scores and ALFF changes in the abovementioned brain regions were not correlated. Taken together, surface-based RS-fMRI can provide more subtle local functional activity to explain the mechanism of tinnitus treatment, and long-term sound therapy had a normalizing effect on tinnitus patients.

Activities of the Right Temporo-Parieto-Occipital Junction Reflect Spatial Hearing Ability in Cochlear Implant Users

Spatial hearing is critical for us not only to orient ourselves in space, but also to follow a conversation with multiple speakers involved in a complex sound environment. The hearing ability of people who suffered from severe sensorineural hearing loss can be restored by cochlear implants (CIs), however, with a large outcome variability. Yet, the causes of the CI performance variability remain incompletely understood. Despite the CI-based restoration of the peripheral auditory input, central auditory processing might still not function fully. Here we developed a multi-modal repetition suppression (MMRS) paradigm that is capable of capturing stimulus property-specific processing, in order to identify the neural correlates of spatial hearing and potential central neural indexes useful for the rehabilitation of sound localization in CI users. To this end, 17 normal hearing and 13 CI participants underwent the MMRS task while their brain activity was recorded with a 256-channel electroencephalography (EEG). The participants were required to discriminate between the probe sound location coming from a horizontal array of loudspeakers. The EEG MMRS response following the probe sound was elicited at various brain regions and at different stages of processing. Interestingly, the more similar this differential MMRS response in the right temporo-parieto-occipital (TPO) junction in CI users was to the normal hearing group, the better was the spatial hearing performance in individual CI users. Based on this finding, we suggest that the differential MMRS response at the right TPO junction could serve as a central neural index for intact or impaired sound localization abilities.

Neuroanatomical aspects of the temporo–parieto–occipital junction and new surgical strategy to preserve the associated tracts in junctional lesion surgery: fiber separation technique

To describe the location of each white matter pathways around the temporo-parieto-occipital junction (TPOJ) and the dissections performed using focal fiber dissection and fiber separation techniques (FST). These areas play an important role in human language processing and high-level brain functions. Thus, it is important to identify the association of the fascicles as well as their courses to plan safe and effective surgical target vectors. Thirty formalin-fixed human hemispheres and two formalin-fixed human heads were dissected with focal fiber dissection and FST under 6-40x magnification using a surgical microscope and real-time magnetic resonance imaging navigation system. Two- and three-dimensional anatomical and surgical pictures were obtained and processed using high dynamic range photography (Photomatix) and were correlated to radiological images of the case with glioblastoma of the TPOJ. The trajectory and connectivity of these fibers as well as their surgical importance in performing FST in cadaver dissections were demonstrated with correlation of the surgical, radiological, and anatomical images. The microanatomy of the TPOJ and related structures, emphasizing the position of each white matter pathway, has been described. Understanding the composition of each region is critical in preventing intraoperative brain injury that could lead to functional deficits.

Tracing short connections of the temporo-parieto-occipital region in the human brain using diffusion spectrum imaging and fiber dissection

The temporo-parieto-occipital (TPO) junction plays a unique role in human high-level neurological functions. Long-range fibers from and to this area have been described in detail but little is known about short TPO tracts mediating local connectivity. In this study, we performed high angular diffusion spectrum imaging (DSI) analyses to visualize the short TPO connections in the human brain. Fiber tracking was conducted on a subject-specific approach (10 subjects) and a template of 90 subjects (NTU-90 Atlas). Three tracts were identified: posterior segment of the superior longitudinal fasciculus (SLF-V), connecting the posterior part of the middle and inferior temporal gyri with the angular gyrus and supramarginal gyrus, vertical occipital fasciculus (VOF), connecting the inferior parietal with the lower temporal and occipital lobe, and a novel temporo-parietal (TP) connection, interconnecting the inferior temporal gyrus, middle temporal gyrus and fusiform gyrus, and inferior occipital lobe with the superior parietal lobe. These studies were complemented by fiber dissection techniques. It is the first study that demonstrated the trajectory and connectivity of the VOF using fiber dissection, as well as displayed the spatial relationship of the SLF-V with the cortex and the adjacent fiber bundles on one dissecting hemisphere. By providing a more accurate and detailed description of the local connectivity of the TPO junction, our findings help to develop new insights into its functional role in the human brain.

Can emotional stress trigger the onset of epilepsy?

The aim of this study was to investigate the potential role of an acute adverse stress as "trigger" for the onset of epilepsy. Among 4618 consecutive patients, twenty-two reported a major life event within three months before the onset of epilepsy. All patients had focal epilepsy except one with idiopathic generalized epilepsy. The temporal lobe was involved in 90% of patients with focal epilepsy. More precisely, 13 patients (62% of patients with focal epilepsy) had medial temporal lobe epilepsy (MTLE), two had lateral temporal lobe epilepsy, four had temporoparietooccipital junction epilepsy, and two patients had central lobe epilepsy. The mean age and the median age at onset of epilepsy for patients with MTLE were both 38 years (range: 9.5-65 years). Ten patients had right and three had left MTLE. Among patients with focal epilepsy, MRI was abnormal in 7 (33%) with hippocampal sclerosis in four, periventricular nodular heterotopia in two, and complex cortical dysgenesis in one. The mean age at onset of epilepsy for patients with brain lesions was 26 years (range: 9.5-49). Twelve patients (54%) reported a death as a triggering factor for the onset of their epilepsy. Seven patients (32%) reported that a relationship of trust had been broken. Three patients (14%) had been subjects of violence. No patient reported sexual abuse as a triggering factor. This study provides evidence that some patients (5/1000 patients) began their seizures in the wake of significant life events. The average age at onset of epilepsy is quite late, around age 30, even in the presence of brain lesions. These patients are emotionally and affectively more prone to have consequences of a stressful life event. The recognition and management of such situations may bring significant relief with improvement of the control of epilepsy.

Crisis epilépticas visuales. Semiología e implicaciones clínicas

Visual phenomena can be symptoms of epileptic seizures, although with an uncertain clinical meaning and relationship with the epileptogenic focus. To describe the clinical implications of visual epileptic seizures according to their signs and symptoms in adults. Data were collected consecutively over a period of one year from patients who reported visual signs and symptoms as the main manifestation of their seizures, and the visual symptoms are classified according to the characteristics of the description. The sample consisted of 78 patients, with a mean age of 43.5 years. Focal epilepsy accounted for 97% of the cases. Of the 63% that were symptomatic epilepsies, 57% were vascular. The visual seizures were, in 81.9% of cases, the aura prior to the seizure, and 17.9% were isolated visual seizures. The coexistence of visual seizures and other types of seizure was associated to pharmacoresistance (p = 0.021). The visual symptoms reported were as follows: simple hallucinations (55.1%), illusions (23.1%), complex hallucinations (15.4%) and loss of vision (6.4%). The lobar localisation of the lesions was occipital (24.4%), temporoparietooccipital (21.8%), temporal (9%), parietal (3.8%) and frontal (1.3%). Occipital lesions were associated with simple visual hallucinations (p < 0.001), and visual illusions and complex visual hallucinations, with lesions affecting the temporoparietooccipital junction (p < 0.05). Of the 55.1% of patients with a unilateral lesion in the magnetic resonance scan, 33% reported symptoms in the contralateral visual hemifield. Visual seizures mainly present as epileptic auras. Simple hallucinations are related with an occipital origin, whereas complex hallucinations are associated with more anterior regions of the brain. The appearance of lateralised visual phenomena suggests an origin located in the contralateral hemisphere.

Illness denial in schizophrenia spectrum disorders: a function of left hemisphere dominance.

Impaired illness awareness or anosognosia is a common, but poorly understood feature of schizophrenia that contributes to medication nonadherence and poor treatment outcomes. Here we present a functional imaging study to measure brain activity at the moment of illness denial. To accomplish this, participants with schizophrenia (n = 18) with varying degrees of illness awareness were confronted with their illness beliefs while undergoing functional MRI. To link structure with function, we explored the relationships among impaired illness awareness and brain activity during the illness denial task with cortical thickness. Impaired illness awareness was associated with increased brain activity in the left temporoparieto-occipital junction (TPO) and left medial prefrontal cortex (mPFC) at the moment of illness denial. Brain activity in the left mPFC appeared to be a function of participants' degree of self-reflectiveness, while the activity in the left TPO was associated with cortical thinning in this region and more specific to illness denial. Participants with impaired illness awareness had slower response times to illness related stimuli than those with good illness awareness. Increased left hemisphere brain activity in association with illness denial is consistent with the literature in other neuropsychiatric conditions attributing anosognosia or impaired illness awareness to left hemisphere dominance. The TPO and mPFC may represent putative targets for noninvasive treatment interventions, such as transcranial magnetic or direct current stimulation.

Intracranial Cortical Responses during Visual–Tactile Integration in Humans

Sensory integration of touch and sight is crucial to perceiving and navigating the environment. While recent evidence from other sensory modality combinations suggests that low-level sensory areas integrate multisensory information at early processing stages, little is known about how the brain combines visual and tactile information. We investigated the dynamics of multisensory integration between vision and touch using the high spatial and temporal resolution of intracranial electrocorticography in humans. We present a novel, two-step metric for defining multisensory integration. The first step compares the sum of the unisensory responses to the bimodal response as multisensory responses. The second step eliminates the possibility that double addition of sensory responses could be misinterpreted as interactions. Using these criteria, averaged local field potentials and high-gamma-band power demonstrate a functional processing cascade whereby sensory integration occurs late, both anatomically and temporally, in the temporo-parieto-occipital junction (TPOJ) and dorsolateral prefrontal cortex. Results further suggest two neurophysiologically distinct and temporally separated integration mechanisms in TPOJ, while providing direct evidence for local suppression as a dominant mechanism for synthesizing visual and tactile input. These results tend to support earlier concepts of multisensory integration as relatively late and centered in tertiary multimodal association cortices.

Brain activity associated with recognition of appropriate action selection based on allocentric perspectives

We investigated brain activity associated with recognition of appropriate action selection based on allocentric perspectives using functional magnetic resonance imaging. The participants observed video clips in which one person (responder) passed one of three objects after a request by a second person (requester). The requester was unable to see one of the three objects because it was occluded by another object. Participants were asked to judge the appropriateness of the responder's action selection based on the visual information from the requester's perspective (i.e., allocentric perspective), not the responder's perspective (i.e., egocentric perspective). The experimental factors included the congruency of request interpretation and the appropriateness of action selection. The results showed that brain regions including the right temporo-parieto-occipital (TPO) junction and the left inferior parietal lobule (IPL) were more activated when the interpretation of the requested object differed between the egocentric and allocentric perspectives than when it was the same (the effect of incongruency for consistency). On the other hand, greater activation was found in the right dorsolateral prefrontal cortex (DLPFC) when the incongruency effect was compared only between the conditions of appropriate action selection (the interaction effect). These results suggest that both the TPO junction and IPL are involved in obtaining visual information from the allocentric perspective when visual information based on only the egocentric perspective is insufficient to interpret another person's request. The right DLPFC is likely related to this process to override the interference of action selection based on the egocentric perspective.

Science Discussion Topic Strategies of Lesion Localization — Reply to Marshall, Fink, Halligan and Vallar

Much to our regret we recognise, that our recently published data and considerations based on these facts were substantially misunderstood in the present comment of John Marshall and colleagues (this volume). First, we must reject the assumption, that our work “confirms that unilateral visuo-spatial neglect can result from lesions of right temporal cortex and from lesion of right parietal cortex”. In fact, we published an analysis of the cortical anatomy of 25 patients with spatial neglect demonstrating a significant area of lesion overlap, that was located in the middle part of the superior temporal gyrus and not in the parietal cortex or the temporo-parieto-occipital (TPO) junction area (Karnath et al., 2001). This outcome is fundamentally different from the hitherto known findings of previous studies on the same topic, recently reviewed by Vallar (2001). Second, and even more important, we never intended to distinguish between several subgroups of neglect patients. A differentiation between “pure spatial neglect” on the one hand and “impure spatial neglect” on the other hand representing two different types of neglect, as put forward here by John Marshall and his colleagues (this volume), is misleading and does not exist in our conclusions and considerations. The term “pure” spatial neglect, that we used in our recent article (Karnath et al., 2001), simply refered to the fact, that patients with neglect included in that study did not suffer from hemianopia, a neurological symptom that is frequently observed in association with hemispatial neglect. Our work was motivated by the fact, that preceding studies on the same topic included a considerable proportion of neglect patients with additional hemianopia. Although hemianopia and hemispatial neglect frequently co-occur, hemianopia obviously represents an unique disorder and cannot be regarded as an integral part of the neglect syndrome. Following an infarct in the vascular territory of the middle cerebral artery (MCA), hemianopia results from damage to the optic radiation. Including a considerable number of neglect patients with additional hemianopia in anatomical studies thus will bias the region of overlap to those areas associated with the occurence of hemianopia, i.e. the subcortical and cortical neural tissue supplied by the posterior branch territory of the MCA. (The cortical tissue that mortifies with such lesions is located in the inferior parietal lobe and the TPO junction area as can be taken, for example, from our recent study that illustrated the lesion overlap in four patients with “pure” hemianopia, i.e. who had only hemianopia after a right MCA infarct without additional spatial neglect.)

Tracing the timing of human analysis of motion and chromatic signals from occipital to temporo-parieto-occipital cortex: a transcranial magnetic stimulation study.

In human visual analysis, the initial processing of motion and chromatic signals may be mediated by feed-forward pathways from striate cortex to segregated areas of extrastriate cortex. The time-course of occipital to temporo-parieto-occipital motion processing was unknown, as was the selectivity of the effect of transcranial magnetic stimulation (TMS) on motion processing. TMS delivered over occipital cortex degraded the discrimination of motion-defined form (MDF) in a discrete time window beginning 100-120 ms from the onset of the visual stimulus. Bilateral focal TMS delivered over the temporo-parieto-occipital junction (TPO) disrupted the discrimination of MDF in a time window beginning 20-40 ms later than the effect of TMS delivered over occipital cortex. Bilateral focal TMS delivered over TPO also degraded the discrimination of CDF, motion direction, and color.