Network Localization of Unconscious Visual Perception in Blindsight.

OBJECTIVE: Blindsight is a disorder where brain injury causes loss of conscious but not unconscious visual perception. Prior studies have produced conflicting results regarding the neuroanatomical pathways involved in this unconscious perception. METHODS: We performed a systematic literature search to identify lesion locations causing visual field loss in patients with blindsight (n = 34) and patients without blindsight (n = 35). Resting state functional connectivity between each lesion location and all other brain voxels was computed using a large connectome database (n = 1,000). Connections significantly associated with blindsight (vs no blindsight) were identified. RESULTS: Functional connectivity between lesion locations and the ipsilesional medial pulvinar was significantly associated with blindsight (family wise error p = 0.029). No significant connectivity differences were found to other brain regions previously implicated in blindsight. This finding was independent of methods (eg, flipping lesions to the left or right) and stimulus type (moving vs static). INTERPRETATION: Connectivity to the ipsilesional medial pulvinar best differentiates lesion locations associated with blindsight versus those without blindsight. Our results align with recent data from animal models and provide insight into the neuroanatomical substrate of unconscious visual abilities in patients. ANN NEUROL 2022;91:217-224.

Characterizing effects of age, sex and psychosis symptoms on thalamocortical functional connectivity in youth.

The thalamus is composed of multiple nuclei densely connected with the cortex in an organized manner, forming parallel thalamocortical networks critical to sensory, motor, and cognitive functioning. Thalamocortical circuit dysfunction has been implicated in multiple neurodevelopmental disorders, including schizophrenia, which also often exhibit sex differences in prevalence, clinical characteristics, and neuropathology. However, very little is known about developmental and sex effects on thalamocortical networks in youth. The present study characterized the effects of age, sex and psychosis symptomatology in anatomically constrained thalamocortical networks in a large community sample of youth (n = 1100, aged 8-21) from the Philadelphia Neurodevelopmental Cohort (PNC). Cortical functional connectivity of seven anatomically defined thalamic nuclear groups were examined: anterior, mediodorsal, ventral lateral, ventral posterolateral, pulvinar, medial and lateral geniculate nuclear groups. Age and sex effects were characterized using complementary thalamic region-of-interest (ROI) to cortical ROI and voxel-wise analyses. Effects of clinical symptomatology were analyzed by separating youth into three groups based on their clinical symptoms; typically developing youth (n = 298), psychosis spectrum youth (n = 320), and youth with other psychopathologies (n = 482). As an exploratory analysis, association with PRIME scores were used as a dimensional measure of psychopathology. Age effects were broadly characterized by decreasing connectivity with sensory/motor cortical areas, and increasing connectivity with heteromodal prefrontal and parietal cortical areas. This pattern was most pronounced for thalamic motor and sensory nuclei. Females showed greater connectivity between multiple thalamic nuclear groups and the visual cortex compared to males, while males showed greater connectivity with the inferior frontal and orbitofrontal cortices. Youth with psychosis spectrum symptoms showed a subtle decrease in thalamic connectivity with the premotor and prefrontal cortices. Across all youth, greater PRIME scores were associated with lower connectivity between the prefrontal cortex and mediodorsal thalamus. By characterizing typical development in anatomically constrained thalamocortical networks, this study provides an anchor for conceptualizing disruptions to the integrity of these networks observed in neurodevelopmental disorders.

The Role of the Thalamus in Post-Traumatic Stress Disorder.

Post-traumatic stress disorder (PTSD) has a high lifetime prevalence and is one of the more serious challenges in mental health care. Fear-conditioned learning involving the amygdala has been thought to be one of the main causative factors; however, recent studies have reported abnormalities in the thalamus of PTSD patients, which may explain the mechanism of interventions such as eye movement desensitization and reprocessing (EMDR). Therefore, I conducted a miniature literature review on the potential contribution of the thalamus to the pathogenesis of PTSD and the validation of therapeutic approaches. As a result, we noticed the importance of the retinotectal pathway (superior colliculus-pulvinar-amygdala connection) and discussed therapeutic indicators.

Severe hypersomnia after unilateral infarction in the pulvinar nucleus- a case report.

BACKGROUND: Although a central role of the thalamus for sleep regulation is undisputed, the exact localization of the crucial structures within the thalamus remains controversial. CASE PRESENTATION: Here we report a 35 year old woman with no prior comorbidities who developed severe and persistent hypersomnia with long sleep time after a small right-sided MRI-verified thalamic stroke affecting the dorsal part of the pulvinar and the dorsolateral boarders of the dorsomedial nuclei. CONCLUSION: The observed symptoms suggest a crucial role of posterior thalamus but not the midline parts of the thalamus in sleep-wake control.

Resting-State Functional Connectivity of the Thalamus in Complete Spinal Cord Injury.

Background. Neuroimaging studies of spinal cord injury (SCI) have mostly examined the functional organization of the cortex, with only limited focus on the subcortical substrates of the injury. However, thalamus is an important modulator and sensory relay that requires investigation at a subnuclei level to gain insight into the neuroplasticity following SCI. Objective. To use resting-state functional magnetic resonance imaging to examine the functional connectivity (FC) of thalamic subnuclei in complete SCI patients. Methods. A seed-based connectivity analysis was applied for 3 thalamic subnuclei: pulvinar, mediodorsal, and ventrolateral nucleus in each hemisphere. A nonparametric 2-sample t test with permutations was applied for each of the 6 thalamic seeds to compute FC differences between 22 healthy controls and 19 complete SCI patients with paraplegia. Results. Connectivity analysis showed a decrease in the FC of the bilateral mediodorsal nucleus with right superior temporal gyrus and anterior cingulate cortex in the SCI group. Similarly, the left ventrolateral nucleus exhibited decreased FC with left superior temporal gyrus in SCI group. In contrast, left pulvinar nucleus demonstrated an increase in FC with left inferior frontal gyrus and left inferior parietal lobule in SCI group. Our findings also indicate a negative relationship between postinjury durations and thalamic FC to regions of sensorimotor and visual cortices, where longer postinjury durations (~12 months) is associated with higher negative connectivity between these regions. Conclusion. This study provides evidence for reorganization in the thalamocortical connections known to be involved in multisensory integration and affective processing, with possible implications in the generation of sensory abnormalities after SCI.

Blue light activates pulvinar nuclei in longstanding idiopathic photophobia: A case report.

Numerous pathologies can contribute to photophobia. When considering light transduction alone, photophobia may be triggered through melanopsin pathways (non-image forming), rod and cone pathways (image-forming), or some combination of the two. We evaluated a 39 year old female patient with longstanding idiopathic photophobia that was exacerbated by blue light, and tested her by presenting visual stimuli in an event-related fMRI experiment. Analysis showed significantly greater activation in bilateral pulvinar nuclei, associated with the melanopsin intrinsically photosensitive retinal ganglion cell (ipRGC) visual pathway, and their activation is consistent with the patient's report that blue light differentially evoked photophobia. This appears to be the first demonstration of functional activation of the ipRGC pathway during photophobia in a patient.

Abnormal thalamocortical network dynamics in migraine.

OBJECTIVE: To investigate the dynamic functional connectivity of thalamocortical networks in interictal migraine patients and whether clinical features are associated with abnormal connectivity. METHODS: We investigated dynamic functional network connectivity (dFNC) of the migraine brain in 89 interictal migraine patients and 70 healthy controls. We focused on the temporal properties of thalamocortical connectivity using sliding window cross-correlation, clustering state analysis, and graph-theory methods. Relationships between clinical symptoms and abnormal dFNC were evaluated using a multivariate linear regression model. RESULTS: Five dFNC brain states were identified to characterize and compare dynamic functional connectivity patterns. We demonstrated that migraineurs spent more time in a strongly interconnected between-network state, but they spent less time in a sparsely connected state. Interestingly, we found that abnormal posterior thalamus (pulvinar nucleus) dFNC with the visual cortex and the precuneus were significantly correlated with headache frequency of migraine. Further topologic measures revealed that migraineurs had significantly lower efficiency of information transfer in both global and local dFNC. CONCLUSION: Our results demonstrated a transient pathologic state with atypical thalamocortical connectivity in migraineurs and extended current findings regarding abnormal thalamocortical networks and dysrhythmia in migraine.

The effect of medial pulvinar stimulation on temporal lobe seizures.

We investigated the effect of electrical stimulation of the medial pulvinar (PuM) in terms of its effect on temporal lobe seizures. Eight patients with drug-resistant temporal lobe epilepsy undergoing stereoelectroencephalographic exploration were included. All had at least one electrode exploring the PuM. High-frequency (50 Hz) stimulations of the PuM were well tolerated in the majority of them. During diagnostic stimulation to confirm the epileptogenic zone, 19 seizures were triggered by stimulating the hippocampus. During some of these seizures, ipsilateral pulvinar stimulation was applied (130 Hz, pulse width = 450 microseconds, duration = 3-7 seconds, 1-2 mA). Compared to non-PuM-stimulated seizures, five of eight patients experienced clinically less severe seizures, particularly in terms of degree of alteration of consciousness. On the electrical level, seizures were more rapidly clonic with a shorter tonic phase. This proof of concept study is the first to suggest that PuM stimulation could be a well-tolerated and effective means of therapeutic deep brain stimulation in drug-resistant epilepsies.

The pulvinar nucleus and antidepressant treatment: dynamic modeling of antidepressant response and remission with ultra-high field functional MRI.

Functional magnetic resonance imaging (fMRI) successfully disentangled neuronal pathophysiology of major depression (MD), but only a few fMRI studies have investigated correlates and predictors of remission. Moreover, most studies have used clinical outcome parameters from two time points, which do not optimally depict differential response times. Therefore, we aimed to detect neuronal correlates of response and remission in an antidepressant treatment study with 7 T fMRI, potentially harnessing advances in detection power and spatial specificity. Moreover, we modeled outcome parameters from multiple study visits during a 12-week antidepressant fMRI study in 26 acute (aMD) patients compared to 36 stable remitted (rMD) patients and 33 healthy control subjects (HC). During an electrical painful stimulation task, significantly higher baseline activity in aMD compared to HC and rMD in the medial thalamic nuclei of the pulvinar was detected (p = 0.004, FWE-corrected), which was reduced by treatment. Moreover, clinical response followed a sigmoid function with a plateau phase in the beginning, a rapid decline and a further plateau at treatment end. By modeling the dynamic speed of response with fMRI-data, perigenual anterior cingulate activity after treatment was significantly associated with antidepressant response (p < 0.001, FWE-corrected). Temporoparietal junction (TPJ) baseline activity significantly predicted non-remission after 2 antidepressant trials (p = 0.005, FWE-corrected). The results underline the importance of the medial thalamus, attention networks in MD and antidepressant treatment. Moreover, by using a sigmoid model, this study provides a novel method to analyze the dynamic nature of response and remission for future trials.

Resting-state pulvinar-posterior parietal decoupling in PTSD and its dissociative subtype.

Key evidence points toward alterations in the neurocircuitry of large-scale networks among patients with posttraumatic stress disorder (PTSD). The pulvinar is a thalamic region displaying reciprocal connectivity with the cortex and has been shown to modulate alpha synchrony to facilitate network communication. During rest, the pulvinar displays functional connectivity with the posterior parietal cortex (PPC), a heteromodal network of brain areas underlying multisensory integration and socioaffective functions that are shown at deficit in PTSD. Accordingly, this study seeks to reveal the resting-state functional connectivity (rsFC) patterns of individuals with PTSD, its dissociative subtype (PTSD + DS) and healthy controls. A whole-brain rsFC analysis was conducted using SPM12 and PickAtlas. Connectivity was analyzed for the left and right pulvinar across groups of individuals with PTSD (n = 81), PTSD + DS (n = 49), and controls (n = 51). As compared to PTSD, controls displayed significantly greater pulvinar rsFC with the superior parietal lobule and precuneus. Moreover, as compared to PTSD + DS, controls showed increased pulvinar connectivity with the superior parietal lobule, inferior parietal lobule and the precuneus. PTSD groups did not display stronger connectivity with any region as compared to controls. Last, PTSD had greater rsFC in the supramarginal gyrus relative to PTSD + DS. Reduced connectivity between the pulvinar and PPC may explain impairments to autobiographical memory, self-referential processing, and socioaffective domains in PTSD and PTSD + DS even at "rest." Critically, these alterations appear to be exacerbated in individuals with PTSD + DS, which may have important implications for treatment.

Blindsight relies on a functional connection between hMT+ and the lateral geniculate nucleus, not the pulvinar.

When the primary visual cortex (V1) is damaged, the principal visual pathway is lost, causing a loss of vision in the opposite visual field. While conscious vision is impaired, patients can still respond to certain images; this is known as 'blindsight'. Recently, a direct anatomical connection between the lateral geniculate nucleus (LGN) and human motion area hMT+ has been implicated in blindsight. However, a functional connection between these structures has not been demonstrated. We quantified functional MRI responses to motion in 14 patients with unilateral V1 damage (with and without blindsight). Patients with blindsight showed significant activity and a preserved sensitivity to speed in motion area hMT+, which was absent in patients without blindsight. We then compared functional connectivity between motion area hMT+ and a number of structures implicated in blindsight, including the ventral pulvinar. Only patients with blindsight showed an intact functional connection with the LGN but not the other structures, supporting a specific functional role for the LGN in blindsight.

Reach and grasp deficits following damage to the dorsal pulvinar.

Expansion of the dorsal pulvinar in humans and its anatomical connectivity suggests its involvement in higher-order cognitive and visuomotor functions. We investigated visuomotor performance in a 31 year old patient (M.B.) with a lesion centered on the medial portion of the dorsal pulvinar (left > right) due to an atypical Sarcoidosis manifestation. Unlike lesions with a vascular etiology, the lesion of M.B. did not include primary sensory or motor thalamic nuclei. Thus, this patient gave us the exceedingly rare opportunity to study the contribution of the dorsal pulvinar to visuomotor behavior in a human without confounding losses in primary sensory or motor domains. We investigated reaching, saccade and visual decision making performance. Patient data in each task was compared to at least seven age matched healthy controls. While saccades were hypometric towards both hemifields, the patient did not show any spatial choice bias or perceptual deficits. At the same time, he exhibited reach and grasp difficulties, which shared features with both, parietal and cerebellar damage. In particular, he had problems to form a precision grip and exhibited reach deficits expressed in decreased accuracy, delayed initiation and prolonged movement durations. Reach deficits were similar in foveal and extrafoveal viewing conditions and in both visual hemifields but were stronger with the right hand. These results suggest that dorsal pulvinar function in humans goes beyond its subscribed role in visual cognition and is critical for the programming of voluntary actions with the hands.

Look me in the eyes: constraining gaze in the eye-region provokes abnormally high subcortical activation in autism.

Individuals with Autism Spectrum Disorder (ASD) seem to have difficulties looking others in the eyes, but the substrate for this behavior is not well understood. The subcortical pathway, which consists of superior colliculus, pulvinar nucleus of the thalamus, and amygdala, enables rapid and automatic face processing. A specific component of this pathway - i.e., the amygdala - has been shown to be abnormally activated in paradigms where individuals had to specifically attend to the eye-region; however, a direct examination of the effect of manipulating the gaze to the eye-regions on all the components of the subcortical system altogether has never been performed. The subcortical system is particularly important as it shapes the functional specialization of the face-processing cortex during development. Using functional MRI, we investigated the effect of constraining gaze in the eye-region during dynamic emotional face perception in groups of participants with ASD and typical controls. We computed differences in activation in the subcortical face processing system (superior colliculus, pulvinar nucleus of the thalamus and amygdala) for the same stimuli seen freely or with the gaze constrained in the eye-region. Our results show that when constrained to look in the eyes, individuals with ASD show abnormally high activation in the subcortical system, which may be at the basis of their eye avoidance in daily life.

Reduced modulation of thalamocortical connectivity during exposure to sensory stimuli in ASD.

Recent evidence for abnormal thalamic connectivity in autism spectrum disorders (ASD) and sensory processing disorders suggests the thalamus may play a role in sensory over-responsivity (SOR), an extreme negative response to sensory stimuli, which is common in ASD. However, there is yet little understanding of changes in thalamic connectivity during exposure to aversive sensory inputs in individuals with ASD. In particular, the pulvinar nucleus of the thalamus is implicated in atypical sensory processing given its role in selective attention, regulation, and sensory integration. This study aimed to examine the role of pulvinar connectivity in ASD during mildly aversive sensory input. Functional magnetic resonance imaging was used to examine connectivity with the pulvinar during exposure to mildly aversive auditory and tactile stimuli in 38 youth (age 9-17; 19 ASD, 19 IQ-matched typically developing (TD)). Parents rated children's SOR severity on two standard scales. Compared to TD, ASD participants displayed aberrant modulation of connectivity between pulvinar and cortex (including sensory-motor and prefrontal regions) during sensory stimulation. In ASD participants, pulvinar-amygdala connectivity was correlated with severity of SOR symptoms. Deficits in modulation of thalamocortical connectivity in youth with ASD may reflect reduced thalamo-cortical inhibition in response to sensory stimulation, which could lead to difficulty filtering out and/or integrating sensory information. An increase in amygdala connectivity with the pulvinar might be partially responsible for deficits in selective attention as the amygdala signals the brain to attend to distracting sensory stimuli. Autism Res 2017, 10: 801-809. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Aberrant pulvinar effective connectivity in generalized social anxiety disorder.

Recent neuroimaging findings in general social anxiety disorder (gSAD) have extended our understanding of the neural mechanisms of gSAD beyond an amygdala-centric fear-based hyperactivity model to include other brain regions and networks relevant to salient cues. In particular, higher order areas compromising visual networks that process emotional and social information have been implicated. The pulvinar anchors this network and is a key regulatory node that mediates complex sensory inputs and the integration between limbic and frontal brain systems. However, the role of the pulvinar and specifically alteration of its effective connectivity with the rest of the brain has not been examined in the pathophysiology of gSAD, a disorder characterized by aberrant socio-emotional processing. The main aim of this study was to examine the pulvinar network effective connectivity in gSAD. In this study, we recruited 21 individuals with gSAD and 19 demographically matched healthy controls (HC), who performed an emotional face processing task while brain activity was recorded using functional magnetic resonance imaging (fMRI). To examine pulvinar-based network dynamics, Granger causality (GC) based effective connectivity (EC) analysis was applied on fMRI data to compare gSAD and HC. The EC analysis revealed heightened casual influential dynamics between pulvinar in higher order visual and frontal regions in gSAD. In conclusion, these preliminary data suggest a novel network-based cortico-pulvino-cortical neural mechanism in the pathophysiology of gSAD.

Pharmacological modulation of pulvinar resting-state regional oscillations and network dynamics in major depression.

The pulvinar, the largest thalamus nucleus, has rich anatomical connections with several different cortical and subcortical regions suggesting its important involvement in high-level cognitive and emotional functions. Unfortunately, pulvinar dysfunction in psychiatric disorders particularly major depression disorder has not been thoroughly examined to date. In this study we explored the alterations in the baseline regional and network activities of the pulvinar in MDD by applying spectral analysis of resting-state oscillatory activity, functional connectivity and directed (effective) connectivity on resting-state fMRI data acquired from 20 healthy controls and 19 participants with MDD. Furthermore, we tested how pharmacological treatment with duloxetine can modulate the measured local and network variables in ten participants who completed treatment. Our results revealed a frequency-band dependent modulation of power spectrum characteristics of pulvinar regional oscillatory activity. At the network level, we found MDD is associated with aberrant causal interactions between pulvinar and several systems including default-mode and posterior insular networks. It was also shown that duloxetine treatment can correct or overcompensate the pathologic network behavior of the pulvinar. In conclusion, we suggest that pulvinar regional baseline oscillatory activity and its resting-state network dynamics are compromised in MDD and can be modulated therapeutically by pharmacological treatment.

Connectivity between the superior colliculus and the amygdala in humans and macaque monkeys: virtual dissection with probabilistic DTI tractography.

It has been suggested that some cortically blind patients can process the emotional valence of visual stimuli via a fast, subcortical pathway from the superior colliculus (SC) that reaches the amygdala via the pulvinar. We provide in vivo evidence for connectivity between the SC and the amygdala via the pulvinar in both humans and rhesus macaques. Probabilistic diffusion tensor imaging tractography revealed a streamlined path that passes dorsolaterally through the pulvinar before arcing rostrally to traverse above the temporal horn of the lateral ventricle and connect to the lateral amygdala. To obviate artifactual connectivity with crossing fibers of the stria terminalis, the stria was also dissected. The putative streamline between the SC and amygdala traverses above the temporal horn dorsal to the stria terminalis and is positioned medial to it in humans and lateral to it in monkeys. The topography of the streamline was examined in relation to lesion anatomy in five patients who had previously participated in behavioral experiments studying the processing of emotionally valenced visual stimuli. The pulvinar lesion interrupted the streamline in two patients who had exhibited contralesional processing deficits and spared the streamline in three patients who had no deficit. Although not definitive, this evidence supports the existence of a subcortical pathway linking the SC with the amygdala in primates. It also provides a necessary bridge between behavioral data obtained in future studies of neurological patients, and any forthcoming evidence from more invasive techniques, such as anatomical tracing studies and electrophysiological investigations only possible in nonhuman species.

From affective blindsight to emotional consciousness.

Following destruction or denervation of the primary visual cortex (V1) cortical blindness ensues. Affective blindsight refers to the uncanny ability of such patients to respond correctly, or above chance level, to visual emotional expressions presented to their blind fields. Fifteen years after its original discovery, affective blindsight still fascinates neuroscientists and philosophers alike, as it offers a unique window on the vestigial properties of our visual system that, though present in the intact brain, tend to be unnoticed or even actively inhibited by conscious processes. Here we review available studies on affective blindsight with the intent to clarify its functional properties, neural bases and theoretical implications. Evidence converges on the role of subcortical structures of old evolutionary origin such as the superior colliculus, the pulvinar and the amygdala in mediating affective blindsight and nonconscious perception of emotions. We conclude that approaching consciousness, and its absence, from the vantage point of emotion processing may uncover important relations between the two phenomena, as consciousness may have evolved as an evolutionary specialization to interact with others and become aware of their social and emotional expressions.

Childhood trauma, midbrain activation and psychotic symptoms in borderline personality disorder.

Childhood trauma is believed to contribute to the development of borderline personality disorder (BPD), however the mechanism by which childhood trauma increases risk for specific symptoms of the disorder is not well understood. Here, we explore the relationship between childhood trauma, brain activation in response to emotional stimuli and psychotic symptoms in BPD. Twenty individuals with a diagnosis of BPD and 16 healthy controls were recruited to undergo a functional MRI scan, during which they viewed images of faces expressing the emotion of fear. Participants also completed the childhood trauma questionnaire (CTQ) and a structured clinical interview. Between-group differences in brain activation to fearful faces were limited to decreased activation in the BPD group in the right cuneus. However, within the BPD group, there was a significant positive correlation between physical abuse scores on the CTQ and BOLD signal in the midbrain, pulvinar and medial frontal gyrus to fearful (versus neutral) faces. In addition there was a significant correlation between midbrain activation and reported psychotic symptoms in the BPD group (P<0.05). These results show that physical abuse in childhood is, in individuals with BPD, associated with significantly increased activation of a network of brain regions including the midbrain in response to emotional stimuli. Sustained differences in the response of the midbrain to emotional stimuli in individuals with BPD who suffered childhood physical abuse may underlie the vulnerability of these patients to developing psychotic symptoms.