Cortical tongue area studied by chronically implanted subdural electrodes—with special reference to parietal motor and frontal sensory responses

Abstract

Motor and sensory cortical tongue representations were examined in 40 patients with intractable seizures who underwent chronic subdural electrode grid implantation. Tongue responses were observed in a wide area 4.5 cm anterior and 3 cm posterior to the central sulcus. The distribution of the responses was not influenced by whether the responses were unilateral or bilateral. In patients with fronto-parietal lesions, the tongue motor area was located significantly more superior to the Sylvian fissure and more anterior to the central sulcus than was the tongue motor area of patients without organic lesion. Both motor and sensory responses were found outside of the classic precentral or postcentral area on the lateral surface of the cortex. Motor responses ('parietal motor responses') could occur posterior to the central sulcus and, rarely, sensory responses ('frontal sensory responses') were identified anterior to the central sulcus. These paradoxical parietal motor and frontal sensory responses were seen in 17 out of 40 (42.5%) patients. Nine of these 17 patients had no organic brain lesion on MRI. Clinical factors, such as patient's age, duration of seizures and cognitive functions (IQ, word fluency score), did not influence the frequency of the paradoxical responses. However, patients with brain lesions showed a tendency to have associated paradoxical responses (P < 0.05). In conclusion, paradoxical responses are not uncommon in epilepsy patients, particularly in those with organic lesions. The physiological and clinical implications of the paradoxical responses are discussed.

Human motor cortex relies on sparse and action-specific activation during laughing, smiling and speech production

“…2a). These observations are consistent with previous ESM research 4,43 and indicate that spatially distant areas are supporting the same effector 19 .…”

“…1a). This is in contrast to the maps of Penfield and Rasmussen 4 , but aligns well with the more recent ESM literature 38,43 . Mouth-related and even hand-related motor representations in sections of Broca’s area (area 44), as we observed here, are not yet known in the context of electrical stimulation studies, but have already been observed in several neuroimaging studies (see review 44 ).…”

Human motor cortex relies on sparse and action-specific activation during laughing, smiling and speech production

“…2a). These observations are consistent with previous ESM research 4,43 and indicate that spatially distant areas are supporting the same effector 19 .…”

“…1a). This is in contrast to the maps of Penfield and Rasmussen 4 , but aligns well with the more recent ESM literature 38,43 . Mouth-related and even hand-related motor representations in sections of Broca’s area (area 44), as we observed here, are not yet known in the context of electrical stimulation studies, but have already been observed in several neuroimaging studies (see review 44 ).…”

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

“…We have also demonstrated a strong positive relationship between seizure duration and the volume of activation to somatosensory stimulation that occurs following seizures. These results are similar to the clinical observations that some people with epilepsy have differently organized sensory maps (Uematsu et al., 1992; Urasaki et al., 1994). Possible mechanisms underlying the observed increase in neurovascular responsiveness include synaptic potentiation and vascular changes.…”

Cortical Activation Induced by Intraoral Stimulation with Water in Humans

“…The shear volume of cortex activated by water is striking. This confirms the disproportionately broad representation of the tongue relative to other body areas, as identified previously in electrophysiological studies (Penfield and Boldrey, 1937;McCarthy et al, 1993;Urasaki et al, 1994). This large volume could not be attributed to spatial blurring since the imaging resolution was <8 mm FWHM.…”

Human motor cortex relies on sparse and action-specific activation during laughing, smiling and speech production

“…2a). These observations are consistent with previous ESM research 4,43 and indicate that spatially distant areas are supporting the same effector 19 .…”

“…1a). This is in contrast to the maps of Penfield and Rasmussen 4 , but aligns well with the more recent ESM literature 38,43 . Mouth-related and even hand-related motor representations in sections of Broca’s area (area 44), as we observed here, are not yet known in the context of electrical stimulation studies, but have already been observed in several neuroimaging studies (see review 44 ).…”

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

“…We have also demonstrated a strong positive relationship between seizure duration and the volume of activation to somatosensory stimulation that occurs following seizures. These results are similar to the clinical observations that some people with epilepsy have differently organized sensory maps (Uematsu et al., 1992; Urasaki et al., 1994). Possible mechanisms underlying the observed increase in neurovascular responsiveness include synaptic potentiation and vascular changes.…”

Cortical Activation Induced by Intraoral Stimulation with Water in Humans

“…The shear volume of cortex activated by water is striking. This confirms the disproportionately broad representation of the tongue relative to other body areas, as identified previously in electrophysiological studies (Penfield and Boldrey, 1937;McCarthy et al, 1993;Urasaki et al, 1994). This large volume could not be attributed to spatial blurring since the imaging resolution was <8 mm FWHM.…”

Human motor cortex relies on sparse and action-specific activation during laughing, smiling and speech production

“…2a). These observations are consistent with previous ESM research 4,43 and indicate that spatially distant areas are supporting the same effector 19 .…”

“…1a). This is in contrast to the maps of Penfield and Rasmussen 4 , but aligns well with the more recent ESM literature 38,43 . Mouth-related and even hand-related motor representations in sections of Broca’s area (area 44), as we observed here, are not yet known in the context of electrical stimulation studies, but have already been observed in several neuroimaging studies (see review 44 ).…”

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

“…We have also demonstrated a strong positive relationship between seizure duration and the volume of activation to somatosensory stimulation that occurs following seizures. These results are similar to the clinical observations that some people with epilepsy have differently organized sensory maps (Uematsu et al., 1992; Urasaki et al., 1994). Possible mechanisms underlying the observed increase in neurovascular responsiveness include synaptic potentiation and vascular changes.…”

Cortical Activation Induced by Intraoral Stimulation with Water in Humans

“…The shear volume of cortex activated by water is striking. This confirms the disproportionately broad representation of the tongue relative to other body areas, as identified previously in electrophysiological studies (Penfield and Boldrey, 1937;McCarthy et al, 1993;Urasaki et al, 1994). This large volume could not be attributed to spatial blurring since the imaging resolution was <8 mm FWHM.…”