Highlighted Findings

Proceeding of the National Academy of Sciences USA (PNAS)

We provide a detailed anatomical tracing of the primate posteromedial cortex (PMC), a term coined for the first time in this publication.

Trends in Cognitive Sciences (TICS)

Documented and highlighted a significant problem in cognitive neuroscience research and coined the term "corticocentric myopia".

Frontiers in Human Neuroscience

Provided an overview of findings from 100 years of intracranial brain stimulation.

Proceeding of the National Academy of Sciences USA (PNAS)

We recorded directly from the PMC in human subjects. This brain region is one of the key hubs of the default mode network (DMN). We uncovered a rapid surge in high-frequency activity within 150ms as the subjects were cued to rest. Specific neuronal populations in the PMC become active immediately upon the onset of the rest condition, i.e., the rest-induced activation in these neurons probably enables mind wandering rather than being the result of mind-wandering per se. Additionally, these rest active neuronal populations did not respond when the subject was actively recollecting autobiographical memories.  

Journal of Neuroscience

A causal connection between electrical stimulation of the human brain and conscious perception was illustrated through an experiment in which stimulation of the face-activated fMRI sites caused clear distortions in face perception.

Current Biology

Shifts in aperiodic brain activity is the principal source of BOLD signals recorded with fMRI.

Journal of Neuroscience

Theta-theta phase coherence between PMC and medial temporal lobe during retrieval of self-referential memory processing.

Nature Communications

Introducing a new method by which we are able to measure local responses in the human brain during naturalistic setting.

Neuron

A causal connection established between electrical stimulation of the human dorsal anterior mid-cingulate cortex and generation of a conscious will / emotion/ derive state.

Journal of Neuroscience

Lateralization of subjective experience: Stimulation of the right hemisphere distorts face perception.

Neuron

First simultaneous recordings across two nodes of the Default Mode Network (DMN) reveal distinct synchronization of activity and intrinsic connectivity during both task engagement and sleep.

Neuron

We demonstrated a clear relationship between the magnitude of electrical charge delivered to a brain area and the size of cortical volume stimulated, and the extent of visual sensations reported by the human subjects.

Neuropsychologia

Lateralization of subjective experience has to do with language lateralization and hand dominance.

Proceeding of the National Academy of Sciences USA (PNAS)

We replicate the same principles of connectivity and synchronized activity across two regions (nodes) of the brain, this time using arithmetic condition as the task of interest.

Journal of Neuroscience

We studied the effect of perturbation of one brain region on other sites of the brain and observed a clear difference in terms of the effect of salience network (SN) stimulation and default mode stimulations: Stimulation of the SN nodes affect other regions of the brain mush faster than the stimulation of the DMN nodes.

Neurology

Stimulation of the ventral PMC causes no changes in the conscious subjective state of the individual.

Epileptic Disorders

Seizures originating in the precuneus (dorsal PMC) clearly distorts the individual patient's subjective sense of space.

Journal of Neuroscience

Simultaneous recordings across different regions of the brain show a clear temporal order of task-evoked activations in dorsal attention network areas of the lateral parietal cortex before deactivations are seen in the medial parietal default mode sites.

Journal of Neuroscience

By employing direct recordings across multiple brain sites and juxtaposing EEG connectivity and resting-state fMRI connectivity measures within the same individuals, we demonstrated that the connectivity observed between two brain regions at rest (as identified through fMRI) is exclusively present between distinct populations of neurons across the two regions.

Epilepsy & Behavior

Even bilateral stimulation of the human claustrum does not cause any changes in the conscious subjective state.

Science Translational Medicine

Epileptic non-lesional brain tissue generates responses to relevant stimuli akin to responses seen in non-epileptic normal brain tissue, but these responses are likely to be "seized" for 100s of milliseconds after the onset of epileptic high frequency oscillations (HFOs).

Social Cognitive and Affective Neuroscience

In three different limbic regions of the brain, we show that the intensity of affective experience is modulated by magnitude of electrical charge delivered to the brain.

Journal of Neuroscience

Changes in the high frequency broadband activity in the dorsal anterior insula, a brain region implicated in salience processing and alertness, are coupled with changes in the pupil diameter during spontaneous resting state as well as salience-detection task.

Nature Communications

We did simultaneous recordings across three regions of interest representing three different brain networks of dorsal attention network (DAN), salience network (SN), and default mode network (DMN). We showed that responses during an attention demanding task appeared fastest in the DAN and then SN sites. Deactivations in the DMN sites occurred significantly later. Lapses of attention (behavioral errors in a demanding task) were marked by distinguishable patterns of both pre- and post-stimulus high frequency activity within each network. Importantly, the magnitude of temporally lagged, negative coupling of such activity between the DAN and DMN (but not SN and DMN) was associated with greater sustained attention performance.

Nature Communications

By recording simultaneously across multiple sites within the inferior temporal cortex, we show that the face stimuli triggered responses in clusters of sites (i.e., anatomically localized neuronal populations). Face-responsive sites showed a posterior to anterior gradient in response time (earlier) and selectivity (more face selective). A sparse model focusing on information from the human face-selective sites performed as well as, or better than, anatomically distributed models when discriminating faces from non-faces stimuli. Additionally, we identified the posterior fusiform site as causally the most relevant node for inducing distortion of conscious face processing by direct electrical stimulation.

Neuron

Ripples (i.e., physiological signature of memory processing in the hippocampus) were documented in the human hippocampus during the retrieval of recent and remote autobiographical events and self-relevant semantic facts. Distributed sites across the neocortical nodes of the default mode network (DMN) exhibited ripple-coupled activations during autobiographical recollection.

Proceeding of the National Academy of Sciences USA (PNAS)

We found that if we electrically stimulate a brain region, the effect of such perturbations is more prominent and faster in other brain regions that are located within the same fMRI-identified resting state network than those across different networks. We then showed that the sites within the same resting state networks (compared to sites across two different networks) respond closer in time during a given cognitive task.

Proceeding of the National Academy of Sciences USA (PNAS)

In a single subject implanted with intracranial electrodes inside the brain, we documented that focal seizures in the anterior precuneus (aPCU) cause distortions in the sense of bodily self and leads to spatial disorientation and loss of spatial perspective.

Brain Stimulation

Electrical stimulations of the ventromedial hypothalamus in a single patient induced profound feeling of shame, sadness, and fear but not rage or anger. When repeated single electrical pulses were delivered to this hypothalamic sites, we recorded significant evoked responses in the amygdala, hippocampus, ventromedial-prefrontal and orbitofrontal, anterior cingulate, and ventral-anterior and dorsal-posterior insula.

Nature Reviews Neuroscience

In this review, we highlight the problem of correlational studies and the importance of causal observations in the neuroscience. We also provide a definition of causal experiments and propose a continuum along which to assess the relative strength of causal information from studies of the human brain.

Brain

We introduce the method of multi-site thalamic recordings and highlight its clinical utility in determining the more prominent thalamic pathway recruited in seizure propagation in each individual patient.

Brain Stimulation

We offer a detailed map of the effects of electrical stimulation of the human insula. We demonstrate that the subjective effects of stimulations align with the cytoarchitectonic maps of the insula.

Journal of Neuroscience

We map the precise temporal sequence of brain-region activations during simple arithmetic using large-scale intracranial EEG. We show that arithmetic processing unfolds as a reliable, orderly cascade across distributed cortical regions, with information progressively transformed along the processing chain.

PNAS

We examine how different brain regions work together when people recall personal memories. We show that memory retrieval follows a reliable sequence of coordinated activity across the thalamus, hippocampus, and cortical regions, with the thalamus helping regulate information flow and the hippocampus helping synchronize communication between areas.

Journal of Neuroscience

We study how parts of the orbitofrontal cortex respond when people think about themselves and evaluate personal traits or memories. We show that these regions activate in a consistent sequence and that reduced brain responses during positive self-judgments are linked to higher levels of depressive symptoms.

Neurosurgery Clinics of North America

In this review, we describe how advances in stereoelectroencephalography have transformed epilepsy monitoring by making it safer, more precise, and better tolerated by patients. We show how SEEG enables a three-dimensional, network-level understanding of seizures and opens the door to more personalized treatments, including mapping seizure spread through the thalamus.

Nature Neuroscience

In this methods paper, we map how the human thalamus and cortex communicate by directly stimulating and recording activity across the brain. We provide a large-scale atlas of thalamocortical interactions and show that different stimulation patterns reveal distinct ways information flows through human brain networks.

Nature Neuroscience

We examine how the insula and hippocampus interact while people form new memories. We show that specific insula activity closely linked to memory success communicates directly with the hippocampus, while other insula responses reflect emotional content but do not contribute to memory encoding.

Journal of Clinical Neurophysiology

We systematically test what happens when the human orbitofrontal cortex is electrically stimulated across a large group of patients. We show that true stimulation of this region rarely produces noticeable subjective experiences, suggesting that many previously reported effects likely came from stimulating nearby brain areas rather than the orbitofrontal cortex itself.

Brain

We examine how the hippocampus communicates with two different thalamic regions within the same human brains. We show that anterior and posterior parts of the hippocampus connect differently to these thalamic nuclei, and that the thalamic regions themselves are strongly interconnected, highlighting a more complex network than previously thought.

PNAS

In this commentary paper, Dr. Parvizi reflects on a newly proposed brain network involved in deciding, acting, and evaluating outcomes, and discusses how these processes may relate to a sense of self. He highlights how this framework brings clarity to previously confusing brain networks and outlines promising directions for future research on action, feedback, and self-related experience in the human brain.

Journal of Cognitive Neuroscience

We describe how clinical care and neuroscience research have been successfully integrated within a large intracranial EEG program over 15 years. We show how this approach has evolved toward safer and more informative recording strategies while advancing both patient care and our understanding of the human brain.

Epilepsia

We compare the subjective experiences caused by insular seizures with those evoked by direct electrical stimulation of the same brain regions. We show that both seizures and stimulation produce similar sensations in consistent insular locations, suggesting a stable map of how the insula gives rise to specific bodily and emotional experiences.