Edward J Tehovnik

Independent

Brain machine interfaces (BMI) have become important in systems neuroscience with the goal to restore motor function in paralyzed patients. We assess the current ability of BMI devices to move objects. The topics discussed include: (1) the bits of information generated by a BMI signal, (2) the limitations of including more neurons for generating a...

Will it be possible for a quadriplegic person equipped with a mechanical exoskeleton to use signals from his brain to kick a ball to open the World Cup? This idea, although appearing very attractive, has generated much controversy. There are five fundamental points that need to be discussed to assess the scientific validity of this idea: (1) The am...

In this review, we examine the importance of having a body as essential for the brain to transfer information about the outside world to generate appropriate motor responses. We discuss the context-dependent conditioning of the motor control neural circuits and its dependence on the completion of feedback loops, which is in close agreement with the...

Subjective, chronic tinnitus that is tonal is a human condition that results in the perception of a continuous sound of a particular frequency, in the absence of that sound, by activation of deafferented portions of the auditory cortex. During ongoing behavior, the brain assumes various states as exemplified by the neural activity at the level of t...

We conduct a comparative evaluation of the visual systems from the retina to the muscles of the mouse and the macaque monkey noting the differences and similarities between these two species. The topics covered include (1) visual-field overlap, (2) visual spatial resolution, (3) V1 cortical point-image [i.e., V1 tissue dedicated to analyzing a unit...

The late Professor Peter H. Schiller of the Massachusetts Institute of Technology is considered one of the best neuroscientists of his generation. Five to six days per week, Peter would arrive at his laboratory at 8:00 am and almost immediately he would be sitting hunched down at his experimental rig setting up his PDP computer files (or an alterna...

Preface to the 3rd Edition (and what is new): Contents of this lecture series have been used to train neuroscientists at the Massachusetts Institute of Technology and at the Baylor College of Medicine. The experiments discussed are based largely on results collected by Drs. Peter H. Schiller and Edward J. Tehovnik, which led to the publication of...

This is a story of my adventures through the Brazilian academic culture. Much of my experience was about the dream of transforming Brazil into a scientific superpower by creating a neuroscience institute in Macaíba, a town located in the northeastern Brazilian state of Rio Grande do Norte. This idea was endorsed by Luiz Inácio Lula da Silva, a pres...

Perhaps, it is no accident that the organ that contains most of the neurons in the human brain, the cerebellum (Herculano-Houzel 2009), is specifically designed to move the body beyond a ‘planted’ location—thereby giving body movement a high priority, a priority that has been shaped by 500 million years of evolution (Cisek 2019). The way in which t...

The following chapters are included: (1) methods, (2) the lateral geniculate nucleus, (3) electrically evoked responses from the striate cortex, (4) the extrastriate cortex (including issues related to the mouse visual cortex), (5) the on and off channels, (6) the midget and parasol systems, (7) color vision, (8) adaptation, (9) motion perception,...

Fast gamma oscillations, generated within the retina, and transmitted to the cortex via the lateral geniculate nucleus (LGN), are thought to carry information about stimulus size and continuity. This hypothesis relies mainly on studies carried out under anesthesia and the extent to which it holds under more naturalistic conditions remains unclear....

We conduct a comparative evaluation of the visual systems from the retina to the muscles of the mouse and the macaque monkey noting the differences and similarities between these two species. The topics covered include (1) visual-field overlap, (2) visual spatial resolution, (3) V1 cortical point-image [i.e., V1 tissue dedicated to analyzing a unit...

The topics covered are: (1) methods, (2) the lateral geniculate nucleus and striate cortex, (3) evoking responses electrically from striate cortex, (4) the extrastriate cortex, (5) the On and Off channels, (6) the Midget and Parasol systems, (7) color vision, (8) adaptation, (9) motion perception, (10) depth perception, (11) pattern vision (object...

Based on two-photon calcium imaging, Histed et al. (2009) concluded that electrical microstimulation of cortical tissue in mammals activates a sparse and distributed population of neurons. This work has been cited by many as proof that electrical microstimulation is non-focal, which means it may lack the precision needed for applications in neuropr...

Brain machine interfaces (BMI) have become important in systems neuroscience with the goal to restore motor function to paralyzed patients. We assess the current ability of BMI devices to move objects. The topics discussed include: (1) the bits of information transferred by a BMI signal, (2) the limitations of including more neurons for generating...

We assess what monkeys see during electrical stimulation of primary visual cortex (area V1) and relate the findings to visual percepts evoked electrically from human V1. Discussed are: (1) the electrical, cytoarchitectonic, and visuo-behavioural factors that affect the ability of monkeys to detect currents in V1; (2) the methods used to ascertain w...

In this article, we review the anatomical inputs and outputs to the mouse primary visual cortex, area V1. Our survey of data from the Allen Institute Mouse Connectivity project indicates that mouse V1 is highly interconnected with both cortical and subcortical brain areas. This pattern of innervation allows for computations that depend on the state...

Here we review the anatomical inputs and outputs to the mouse primary visual cortex, area V1. Our survey of data from the Allen Institute Mouse Connectivity Project indicates that mouse V1 is highly interconnected with both cortical and subcortical brain areas. This pattern of innervation allows for computations that depend on the state of the anim...

Gamma oscillations in the retina are transmitted to the lateral geniculate nucleus (LGN) and to the cortex, and are thought to encode stimulus size and continuity. Support for these conjectures were obtained mostly in the anesthetized cat, and visual stimuli were often limited to whole-field flashes. Here, we aim filling this gap by characterizing...

VISION AND THE VISUAL SYSTEM by Peter H. Schiller and Edward J. Tehovnik This book provides the essential facts about how visual information is processed in the brain. There are 16 chapters. Chapter 1 provides basic information about the methods used by investigators to deduce how visual information is processed in living organisms with an emphasi...

Title: Myth and Reality behind AVATAR: Brain-Machine Interfaces. Speaker: Edward J Tehovnik Institution: Brain Institute, UFRN, Natal, RN, Brazil. Funding: CNPq (Brazilian gov’t funding) Main topics to be discussed: Brain machine interfaces have become important in rehabilitation with the goal to restore motor function to paralyzed people. I wi...

Chen LL, Tehovnik EJ, May PJ. Does the brain compute the future or the present? OA Neurosciences 2014 Apr 10;2(1):7. Short Communication A recent study employed an oculomotor version of the sport of baseball to test two competing hypotheses: the dual-drive and single-drive theories. The findings were consistent with other recent studies, supporti...

As the world cup fast approaches there is much discussion on the scientific merit of having a paralyzed individual use a robotic exoskeleton to kick a ball to open the FIFA World Cup in São Paulo on June 12 (Regalado 2014). This event is being orchestrated by Prof. Miguel Nicolelis who has been able to obtain monies from the Brazilian government—so...

Brain-to-brain transfer of information has been illustrated between a pair of rats. We evaluate the scientific validity of this study. First, the rats receiving the electrical stimulation were performing at 62% to 64% correctness, when chance was 50% correctness using one of the two discrimination paradigms, tactile or visual. This level of perform...

O QUE FAZER COM O CIENTISTA BRASILEIRO DE INTELECTO SUPER-IOR? Edward J Tehovnik, Zivanilson Teixeira e Silva, UFRN, Natal, RN, Brazil, tehovnikej@gmail.com, Feb 2014. Como a maioria dos brasileiros estão sabendo, no dia 12 de junho deste ano, uma criança paralítica ligada à um exoesqueleto robótico vai abrir o campeonato mundial da FIFA, utilizan...

Between 2010 and 2012, I had the pleasure of working at the Edmond and Lily Safra International Institute of Neuroscience of Natal (ELS-IINN). Under the supervision of Drs. Romulo Fuentes and Miguel Nicolelis, we were investigating the possibility of extending the work of Fuentes et al. (2009) as published in Science magazine. In the Science articl...

Brain machine interfaces (BMI) have become important in systems neuroscience with the goal to restore motor function in paralyzed patients. We assess the current ability of BMI devices to move objects. The topics discussed include: (1) the bits of information generated by a BMI signal, (2) the limitations of including more neurons for generating a...

July 2013. Techniques have been developed for monitoring, activating, and inhibiting neural activity using optical methods (Bernstein et al. 2012; Soham and Deisseroth 2010). These techniques are fast complementing and in time may even replace conventional recording, stimulation, and lesion methods employed in visual neuroscience. Optical stimulati...

Denk et al. (1990) were the first to show that two-photon excitation could be used to image fluorescently stained living cells and cellular substructures (Kerr and Denk 2008). Much like optical imaging, two-photon imaging is used to study the activity of cells close to the surface of the brain (Ohki et al. 2005, 2006; Stosiek et al. 2003). However,...

Based on two-photon calcium imaging, Histed et al. (2009) concluded that electrical microstimulation of cortical tissue in mammals activates a sparse and distributed population of neurons. This work has been cited by many as proof that electrical microstimulation is nonfocal, which means it may lack the precision needed for applications in neuropro...

Creating a prosthetic device for the blind is a central future task. Our research examines the feasibility of producing a prosthetic device based on electrical stimulation of primary visual cortex (area V1), an area that remains intact for many years after loss of vision attributable to damage to the eyes. As an initial step in this effort, we beli...

In work reported last year at this meeting we had shown that subthreshold microstimulation in V1, V2, LIP, FEF and MEF of monkeys can variously produce facilitation, interference, and delays in saccade initiation, thereby identifying some of the essential neural computations carried out in the process of target selection with saccadic eye movements...

The cortical control of visually guided saccadic eye movements is accomplished through two major interactive systems, the anterior and the posterior. The posterior system from the occipital and parietal cortices reaches the brain stem oculomotor centers through the superior colliculus and plays a central role in the generation of short-latency sacc...

Monkeys detect electrical microstimulation delivered to the striate cortex (area V1). We examined whether the ability of monkeys to detect such stimulation is affected by background luminance. While remaining fixated on a spot of light centered on a monitor, a monkey was required to detect a 100 ms train of electrical stimulation delivered to a sit...

Monkeys can detect electrical stimulation delivered to the striate cortex (area V1). We examined whether such stimulation is layer dependent. While remaining fixated on a spot of light, a rhesus monkey was required to detect a 100-ms train of electrical stimulation delivered to a site within area V1. A monkey signaled the delivery of stimulation by...

This review argues that one reason why a functional visuo-cortical prosthetic device has not been developed to restore even minimal vision to blind individuals is because there is no animal model to guide the design and development of such a device. Over the past 8 years we have been conducting electrical microstimulation experiments on alert behav...

In this study, we examined procedures that alter saccadic latencies and target selection to visual stimuli and electrical stimulation of area V1 in the monkey. It has been shown that saccadic eye movement latencies to singly presented visual targets form a bimodal distribution when the fixation spot is turned off a number of milliseconds prior to t...

There are more than forty million blind individuals in the world whose plight would be greatly ameliorated by creating a visual prosthesis. We begin by outlining the basic operational characteristics of the visual system, as this knowledge is essential for producing a prosthetic device based on electrical stimulation through arrays of implanted ele...

It is well known that electrical activation of striate cortex (area V1) can disrupt visual behavior. Based on this knowledge, we discovered that electrical microstimulation of V1 in macaque monkeys delays saccadic eye movements when made to visual targets located in the receptive field of the stimulated neurons. This review discusses the following...

Electrical microstimulation of macaque V1 has previously been shown to delay saccadic eye movements made to a punctate visual target placed in the receptive field of the stimulated neurons. It remains unclear whether this delay effect is specific to the oculomotor system or whether the effect can be demonstrated in the skeletomotor system as well....

The cortical control of eye movements is well known. It remains unclear, however, as to how the eye fields of the frontal lobes generate and coordinate eye and head movements. Here, we review the recent advances in electrical stimulation studies and evaluate relevant models. As electrical stimulation is conducted in head-unrestrained, behaving subj...

Non-human primates are being used to develop a cortical visual prosthesis for the blind. We use the properties of electrical microstimulation of striate cortex (area V1) of macaque monkeys to make inferences about phosphene induction. Our analysis is based on well-established properties of V1: retino-cortical magnification factor, receptive-field s...

Electrical microstimulation of macaque striate cortex (area V1) delays the execution of saccadic eye movements made to a visual target placed in the receptive field of the stimulated neurons. The region of visual space within which saccades are delayed is called a delay field. We examined the effects of changing the parameters of stimulation and ta...

Electrical microstimulation has been used to elucidate cortical function. This review discusses neuronal excitability and effective current spread estimated by using three different methods: 1) single-cell recording, 2) behavioral methods, and 3) functional magnetic resonance imaging (fMRI). The excitability properties of the stimulated elements in...

We examined the effects of electrical stimulation of area V1 in the monkey to determine the feasibility of using implanted electrode arrays as a visual prosthesis. Area V1 in the monkey is lissencephalic making for easy access; the visual field is laid out topographically and the receptive fields of the neurons are quite small. Our experiments show...

Over the last two centuries, electrical microstimulation has been used to demonstrate causal links between neural activity and specific behaviors and cognitive functions. However, to establish these links it is imperative to characterize the cortical activity patterns that are elicited by stimulation locally around the electrode and in other functi...

Electrical microstimulation of macaque primary visual cortex (area V1) is known to delay the execution of saccadic eye movements made to a punctate visual target placed into the receptive field of the stimulated neurons. We examined the spatial extent of this delay effect, which we call a delay field, by placing a 0.2 degrees visual target at vario...

Electrical microstimulation of the striate cortex (area V1) in monkeys delays the execution of saccadic eye movements generated to a visual target located in the receptive field of the stimulated neurons. We have argued that this effect is because of disruption of the visual signal transmitted along the geniculostriate pathway. The delivery of elec...

In exploring the visual scene we make about three saccadic eye movements per second. During each fixation, in addition to analyzing the object at which we are looking, a decision has to be made as to where to look next. Although we perform this task with the greatest of ease, the computations to perform the task are complex and involve numerous bra...

The purpose of this review is to critically examine phosphene induction and saccadic eye movement generation by electrical microstimulation of striate cortex (area V1) in humans and monkeys. The following issues are addressed: 1) Properties of electrical stimulation as they pertain to the activation of V1 elements; 2) the induction of phosphenes in...

Electrical microstimulation delivered to primary visual cortex (V1) concurrently with the presentation of visual targets interferes with the selection of these targets. To determine the source of this interference, we stimulated the visual input layers of V1 as rhesus monkeys generated saccadic eye movements to visual targets presented at and outsi...

Electrical stimulation delivered to V1 concurrently with the presentation of a visual target interferes with both the selection and the detection of targets positioned in the receptive field of the stimulated neurons. In the present study, we examined the temporal course of this effect by delivering electrical stimulation to V1 of rhesus monkeys at...

Reviewed is how behavioural context influences saccadic eye movements elicited electrically from the neocortex of monkeys. Factors found to affect stimulation-evoked saccades include (1) motor state, i.e. whether stimulation is delivered during free-viewing, or during or after active fixation, or before an animal is about to execute a saccade to a...

The role inhibitory circuits play in target selection with saccadic eye movements was examined in area V1, the frontal eye fields (FEF) and the lateral intraparietal sulcus (LIP) of the Rhesus Macaque monkey by making local infusions of the GABA agonist muscimol and antagonist bicuculline. In V1, both agents greatly interfered with target selection...

The goal of this study was to use the ocular dominance properties of multiple unit activity in area V1 of the visual cortex of the behaving rhesus monkey to infer the depth of the visual input layers. Multiple unit activity was examined with a recording electrode at different depths (in 100 micrometer increments) within V1 for responses to a visual...

Experiments were performed to assess the excitability of neural elements activated while inducing saccadic eye movements electrically from different cortical layers of striate cortex (area V1) in rhesus monkeys. Excitability was assessed by measuring current thresholds, saccadic latencies, chronaxies, and the effectiveness of anode-first vs. cathod...

Microstimulation of the intermediate layers of V1 in rhesus monkeys disrupts target selection with saccadic eye movements. To study target selection, one visual target was presented in the receptive-field location of the stimulated neurons and a second target was presented outside this location. Microstimulation delivered with the appearance of the...

In work reported last year at this meeting we had shown that subthreshold microstimulation in V1, V2, LIP, FEF and MEF of monkeys can variously produce facilitation, interference, and delays in saccade initiation, thereby identifying some of the essential neural computations carried out in the process of target selection with saccadic eye movements...

We explored the effects of microstimulation on target selection by delivering stimulation at different depths within V1 (striate cortex) of the rhesus monkey (Macaca mulatta). Stimulation evoked saccadic eye movements that terminated in the receptive-field location of the activated neurons. The current thresholds for saccade evocation were highest...

Electrical stimulation of superficial V1 (layers I through IV) interrupts a monkey's ability to select visual targets appearing in the receptive field region of the stimulated neurons, whereas stimulation of the deep V1 (layers V and VI) tends to drive the eyes toward the target (Schiller and Tehovnik 2001). Given this functional segregation betwee...

Two major cortical streams are involved in the generation of visually guided saccadic eye movements: the anterior and the posterior. The anterior stream from the frontal and medial eye fields has direct access to brainstem oculomotor centers. The posterior stream from the occipital cortices reaches brainstem oculomotor centers through the superior...

The receptive field, defined as the spatiotemporal selectivity of neurons to sensory stimuli, is central to our understanding of the neuronal mechanisms of perception. However, despite the fact that eye movements are critical during normal vision, the influence of eye movements on the structure of receptive fields has never been characterized. Here...

Two major cortical streams are involved in the generation of visually guided saccadic eye movements: the anterior and the posterior. The anterior stream from the frontal and medial eye fields has direct access to brainstem oculomotor centers. The posterior stream from the occipital cortices reaches brainstem oculomotor centers through the superior...

It has been reported that training affects motor responses evoked electrically from the dorsomedial frontal cortex (DMFC). Once a monkey had been trained to generate visually-guided saccadic eye movements of a particular size and direction, electrical stimulation of the DMFC elicited saccades of only that size and direction [7]. The current study r...