Persistent enhancement of functional MRI responsiveness to sensory stimulation following repeated seizures

• Published in: Epilepsia (Copenhagen) Vol. 52; no. 12; pp. 2285 - 2292
• Main Authors: Vuong, Jennifer, Henderson, Amy K., Tuor, Ursula I., Dunn, Jeff F., Teskey, G. Campbell
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.12.2011; Wiley-Blackwell; Wiley Subscription Services, Inc
• Subjects: Afferent Pathways - physiopathology; Animals; Behavior; Biological and medical sciences; Brain; Brain mapping; Carbon; Corpus callosum; Corpus Callosum - physiopathology; Cortex; Cortex (motor); Cortex (somatosensory); Electric Stimulation - adverse effects; Electrical stimuli; Electrodes; Electroencephalography; Epilepsy; Fibers; Forelimb - physiopathology; Forepaw stimulation; Functional Laterality; Functional magnetic resonance imaging; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Image Processing, Computer-Assisted; Investigative techniques, diagnostic techniques (general aspects); Kindling; Magnetic Resonance Imaging; Male; Medical sciences; Nervous system; Nervous system (semeiology, syndromes); Neuroimaging; Neurology; Oxygen - blood; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Rats; Rats, Long-Evans; Rodents; Seizure; Seizures; Seizures - etiology; Seizures - pathology; Sensorimotor cortex; sensorimotor system; Somatosensory Cortex - blood supply; Somatosensory Cortex - physiopathology; Time Factors; Nervous system diseases; Kindling; Epilepsy; Central nervous system; Nuclear magnetic resonance imaging; Encephalon; Cerebral disorder; Convulsion; Central nervous system disease; Forepaw stimulation; Sensorimotor cortex; Functional magnetic resonance imaging; Seizure; Neurological disorder; Functional imaging
• ISSN: 0013-9580; 1528-1167
• DOI: 10.1111/j.1528-1167.2011.03317.x

Summary Purpose:  Neural reorganization and interictal behavioral anomalies have been documented in people with epilepsy and in animal seizure models. Alterations in behavior could be due to somatosensory dysfunction. This study was designed to determine whether seizures can lead to changes in somatosensory representations and whether those changes are persistent. Methods:  Twice‐daily seizures were elicited by delivering 1 s of electrical stimulation through carbon fiber electrodes implanted in both the corpus callosum and sensorimotor neocortex of young adult male Long‐Evans rats until a total of 20 seizures were elicited. Either 1–3 days or 3–5 weeks following the last seizure, functional magnetic resonance imaging (MRI) was used to image the brain during electrical stimulation of each forepaw independently. Key Findings:  Forepaw stimulation in control rats resulted in a focused and contralateral fMRI signal in the somatosensory neocortex. Rats that had repeated seizures had a 151% increase in the number of voxels activated in the contralateral hemisphere 1–3 days after the last seizure and a 166% increase at 3–5 weeks after the last seizure. The number of voxels activated in response to forepaw stimulation was positively correlated with the duration of the longest seizure experienced by each rat. The intensity of the activated voxels was not significantly increased at either time interval from the last seizure. Significance:  The increased area of activation in somatosensory cortex, which is persistent at 3–5 weeks, is consistent with previous observations of larger motor maps following seizures. Seizure‐induced changes in the functioning of sensory cortex may also contribute to interictal behavioral anomalies.