2. Perceiving

Do you need to recognize an object to know how to handle it? Why do some amputees continue to feel their arm even though it is absent? Why do some people see colours when they read or hear words? ‘Perceiving’ considers these questions and then provides the background information to answer them. It explains that the brain is not a single pathway from input to output, but that there are separate pathways and that pathways diverge. The different regions of the brain—such as the ventral and dorsal systems and primary sensory area—are explained in terms of how they are used for the recognition and classification of objects, and for perceptual awareness.

Epileptic seizure propagation from the second somatic sensory area to the fronto-medial region, by insular redistribution. A case report and a connectome description

SUMMARY Introduction. The seizure propagation phenomenon by inducing remote symptoms brings several difficulties in finding the seizure onset and delineating the epileptic network which should be taken into consideration in epilepsy surgery. By demonstrating a difficult (MRI negative) epilepsy surgery case explored with invasive presurgical evaluation we highlight the importance to recognise the secondary sensory area and to explore the the parieto-opercular-insular-medial frontal network in certain cases. A further conclusion is the consideration of the redistributory role of the insula as a special structure in the cerebral connectome, having a role in epileptic network organisation. Aims. To support the role of the insula in the organisation of an opercular – medial frontal epileptic network and to confirm Penfield’s the “second somatic sensory leg area” by way of a case report. We try to give an up to date exploration of our patient’s remote epileptic seizures by way of a connectome. Methods. The epileptic disorder was studied with intensive video EEG monitoring and two times 3T MRI. Interictal FDG (fluorodeoxyglucose) PET was also undertaken. Beside the scalp EEG and computerized frequency analysis, the evaluation was performed by invasive EEG with 2 grids and 2 strips and an insular deep electrode in addition. Electrical cortical stimulation and cortical mapping were also undertaken. Results. The video-EEG study revealed the complex seizure semiology. The left sided global somatosesensory aura in the leg, followed supplementary motor area manifestations represented a remote seizure. The seizure onset zone and the symptomatogenic zone were localised by the invasive electrophysiology. With the insular deep electrode we succeeded to explore the propagation of ictal activity to the insula and later to frontal medial surface. The PET, the negative 3T MRI results and the postprocessing morphometry confirmed the lesional origin and localised the epileptogenic area to the second somato-sensory field where a dysgenesis was located. Conclusions. By preoperative invasive video-EEG evaluation, the second somato-sensory leg area was delineated as the seizure onset zone. The resection of this area by IIb type cortical dysgenesis, resulted in a complete relief of the seizures. The invasive video-EEG revealed the peculiar role of the insula in the propagation of the epileptic seizure from the second sensory leg area to the ipsilateral fronto-medial supplemetary motor area. Our results, confirm, that the insula has a relay or node function on the parietal opercular-fronto-medial epileptic network. The connectome of the insula is a further additive of the scale-free features of the remote epileptic networks.

Postmitotic regulation of sensory area patterning in the mammalian neocortex by Lhx2

Current knowledge suggests that cortical sensory area identity is controlled by transcription factors (TFs) that specify area features in progenitor cells and subsequently their progeny in a one-step process. However, how neurons acquire and maintain these features is unclear. We have used conditional inactivation restricted to postmitotic cortical neurons in mice to investigate the role of the TF LIM homeobox 2 (Lhx2) in this process and report that in conditional mutant cortices area patterning is normal in progenitors but strongly affected in cortical plate (CP) neurons. We show that Lhx2 controls neocortical area patterning by regulating downstream genetic and epigenetic regulators that drive the acquisition of molecular properties in CP neurons. Our results question a strict hierarchy in which progenitors dominate area identity, suggesting a novel and more comprehensive two-step model of area patterning: In progenitors, patterning TFs prespecify sensory area blueprints. Sequentially, sustained function of alignment TFs, including Lhx2, is essential to maintain and to translate the blueprints into functional sensory area properties in cortical neurons postmitotically. Our results reemphasize critical roles for Lhx2 that acts as one of the terminal selector genes in controlling principal properties of neurons.

The Left Superior Longitudinal Fasciculus within the Primary Sensory Area of Inferior Parietal Lobe Plays a Role in Dysgraphia of Kana Omission within Sentences

Functional neurological changes after surgery combined with diffusion tensor imaging (DTI) tractography can directly provide evidence of anatomical localization of brain function. Using these techniques, a patient with dysgraphia before surgery was analyzed at our hospital in 2011. The patient showed omission of kana within sentences before surgery, which improved after surgery. The brain tumor was relatively small and was located within the primary sensory area (S1) of the inferior parietal lobe (IPL). DTI tractography before surgery revealed compression of the branch of the superior longitudinal fasciculus (SLF) by the brain tumor. These results suggest that the left SLF within the S1 of IPL plays a role in the development of dysgraphia of kana omission within sentences.