The overarching goal of the lab is to study the temporal dynamics and the compensatory physiological and behavioral responses of the visual system using noninvasive brain stimulation coupled with functional imaging and behavioral psychophysical testing.
The work in our research lab focuses on the study of attentional functions in the healthy and diseased brain. Specifically, we have performed studies of inter- and intra-hemispheric connectivity, its impairment in stroke and its recovery after noninvasive brain stimulation as therapeutic treatment. In addition to brain stimulation and behavioral measures, we perform MRI analysis of both intact and neurologically impaired subjects. Finally, we apply noninvasive brain stimulation either for focally perturbing or enhancing brain functions in healthy subjects.
- Emily Grossman
- Duje Tadin
- Krystel Huxlin
- Aaron Seitz
- Sara Mednick
- Clayton Hickey
- Alex Holcombe
- George Alvarez
- Anna Montagnini
- Alfonso Caramazza
Time perception: how does the visual system interpret a coherent, integrated percept of motion in dynamic visual scenes?
The main question we ask is: how does the visual system analyze the complex visual environments? What happens when these processes go away after cortical strokes? As part of our studies, we examine neurological patients affected by stroke involving cortical areas. We have discovered that unilateral right parietal stroke patients show a severe visual deficit in a simple apparent motion task, but are unaffected in low- level (smooth) motion tasks. Based on these and other findings, we proposed a new theory: that visual relative timing, and perhaps relative timing in general, is a specialized function of the right inferior parietal lobe. In a series of papers, we hypothesized that relative timing impairments could broadly underlie many of the perceptual and attentional deficits in patients with parietal lesions.
Sustained attention: perturb-and- measure the neurophysiological substrates of visual attention
Another function of the parietal lobe we are interested in is attentional tracking. Our work has provided direct evidence that the two parietal lobes compete with each other during sustained attention. In a set of experiments, we used combined fMRI and rTMS to study the cortical networks involved in attentional tracking. We used 1-Hz rTMS over the parietal cortex to study the dynamic interplay across cortical attention networks in the brain of normal subjects. Low frequency rTMS temporarily mimics the behavioral effects of parietal stroke, and in our study, we compared brain activity after active versus sham stimulation using fMRI. Our studies demonstrated the feasibility of using fMRI immediately following a single session of rTMS to detect temporary changes in neural activity throughout the neural network involved in sustained attention. The data also suggest the intriguing possibility that rTMS could be used to treat and improve attentional functions in unilateral stroke patients.
Restoring attentional functions in parietal stroke patients
Our combined rTMS-fMRI experiments have led the lab work into new and exciting directions. Our findings suggested that the two cortical hemispheres inhibit one another during normal brain function. It follows that if one hemisphere is inactivated or damaged, its reduced activity could disinhibit the opposite (healthy) hemisphere, leading to abnormally increased activity in the healthy hemisphere that in turn overly-inhibits the lesioned hemisphere. This hypothesis suggested a strategy to treat attentional deficits: reduce the over-activity of the healthy, contra-lesional hemisphere by applying inhibitory rTMS, thus reducing the excess inhibition of the lesioned hemisphere, leading to improved attentional function. We have used rTMS as a rehabilitation technique in patients affected by visual neglect and extinction. Our studies established a proof-of-principle for using neuromodulation as a tool to boost cognitive and motor functions.
Biological motion: how the visual system interprets complex visual motion?
In the laboratory, we have explored the cortical mechanisms involved in the integration of visual information across space and time. We have addressed the question of how the visual system interprets the integrated form and motion of patterns of point-lights that describe bodily forms, so-called biological motion. We demonstrated that inhibitory rTMS over a visual associative area (the superior temporal sulcus) in healthy subjects impaired biological motion perception. Finally, we have used rTMS to examine the visual cortical mechanisms responsible for actively suppressing irrelevant information in the background to enhance processing of relevant foreground objects. It had been previously found that this function is less efficient in the elderly and in certain psychiatric conditions, such as depression and schizophrenia. Our results demonstrated the middle temporal visual area (MT) plays a fundamental role in visual integration as well as in other functions.
The lab is equipped with: a) three transcranial magnetic stimulations (single pulse and repetitive) (TMS, Magstim Rapid 2 100Hz); b) high-density EEG recording system with concurrent frameless stereotaxy-guided TMS (NeuroConn); c) frameless stereotactic system (Brainsight, Rogue, Inc.). d) three transcranial electrical stimulation devices (tES, NeuroConn). e) several computers having the necessary software to allow data entry and documentation, statistical analysis, graphical display of the results, and image processing and analysis.
Contralesional rTMS relieves visual extinction in chronic stroke. Agosta S., Herpich F., Miceli G., Ferraro F. and Battelli L. Neuropsychologia: 62:269-76. (2014)
The Pivotal Role of the Right Parietal Lobe in Temporal Attention. Agosta S, Magnago D, Tyler S, Grossman E, Galante E, Ferraro F, Mazzini N, Miceli G, Battelli L Journal of Cognitive Neuroscience. 19:1-11. (2016)
The When pathway of the right parietal lobe. Battelli L., Pascual Leone A. and Cavanagh P. Trends in Cognitive Sciences, 11(5): 204-210. (2007)
The role of the parietal lobe in visual extinction studied with transcranial magnetic stimulation. Battelli L, Alvarez G, Carlson T and Pascual-Leone Journal of Cognitive Neuroscience. (2009)
Local Immediate versus Long-Range Delayed Changes in Functional Connectivity Following rTMS on the Visual Attention Network. Battelli L, Grossman ED, Plow EB. Brain Stimulation (2017)
Distinct neural mechanisms for body form and body motion discriminations. Vangeneugden J, Peelen MV, Tadin D and Battelli L. Journal of Neuroscience. 8;34(2):574-85. (2014)