Mapping The Cerebral Cortex
Andrew P. Wickens in A History of the Brain, 2014
Among Ferrier’s many discoveries was the existence, in the monkey at least, of areas mediating movement that lay outside the boundaries of the frontal cortex. One of these sites was the upper part of the temporal lobes which lay adjacent to the Sylvian fissure20 (i.e. a region lying roughly behind the ears). When Ferrier stimulated this area with an electric current, it produced a sudden turning of the head that resembled a response of an animal startled by an unexpected sound. It was a reaction implying a part of the temporal lobes might be involved in hearing, and to examine this possibility further, Ferrier bilaterally lesioned the region in monkeys, and tested their reaction to a variety of stimuli. He found the monkeys were completely unresponsive to sound – a finding confirmed when two animals with unilateral lesions were shown to be deaf in only one ear. Thus, Ferrier had apparently managed to localise the function of hearing to the upper temporal cortex.
Perception of Sounds at the Auditory Cortex
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
The classic study of Geschwind and Levitsky8 alerted us to the concept of anatomical differences between the left and right sides of the planum temporale (see Figure 50.2). This study and many subsequent studies have shown that in normal brains the left planum temporale is significantly larger than its right-sided counterpart. There is also anatomical evidence that is definitely slanted towards the Sylvian fissure being longer and more horizontal on the left than the right side of the brain.2,9 In regard to Heschl’s gyrus there is also evidence supporting a left-sided size advantage, but this is not without some exceptions that point to both left and right Heschl’s being similar in size.1,2,10,11 The existence of asymmetries for the core–belt orientation is, at least for the present authors, difficult to glean from the literature and requires more investigation before a definitive determination of the existence of any asymmetries (or lack thereof) can be rendered. This lack of information regarding asymmetries in the core–belt areas is due in part to the lack of understanding of the borders of the core–belt designation as it applies to humans.
Anatomy for neurotrauma
Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor in Essentials of Anesthesia for Neurotrauma, 2018
The cerebral cortex is folded into numerous convolutions called gyri, separated by fissures or sulci, for accommodation in a limited space within the skull, rendering the cortex a massive surface area of around 2200 square centimeters. The lateral sulcus (Sylvian fissure), and the central sulcus (Rolandic fissure), along with an imaginary line connecting the parieto-occipital sulcus to the preoccipital notch, divide the cerebral hemisphere into four lobes—the frontal, parietal, temporal, and occipital. The frontal lobe lies anterior to the central sulcus and above the lateral sulcus; the parietal lobe lies behind the central sulcus and above the lateral sulcus; the temporal lobe is below the lateral sulcus; and the occipital lobe lies below and behind the imaginary line from the parieto-occipital sulcus to the preoccipital notch.
Spontaneous neonatal subdural haemorrhage: always non-accidental injury?
Published in British Journal of Neurosurgery, 2020
Adikarige Haritha Dulanka Silva, Lara Gander, Haren Wijesinghe, Desiderio Rodrigues
Owing to further deterioration a decision was made for surgical evacuation of a presumed traumatic ASDH. On reviewing the imaging, some of the subdural bleeding was observed to be extending into the Sylvian fissure, raising suspicion that the haemorrhage was extending and emanating from a possible underlying vascular lesion. This was in the absence of other more typical features of aneurysmal haemorrhage such as florid subarachnoid haemorrhage, intracerebral haemorrhage or intraventricular haemorrhage. Magnetic resonance angiography (MRA) and conventional catheter digital subtraction cerebral angiography (DSA) was performed, confirming the presence of a ruptured saccular aneurysm (11 × 11 × 11 mm in all dimensions) located distally on the opercular segment of the left MCA (M3) (Figure 2). Onyx embolisation of the aneurysm was performed followed by emergency craniotomy and evacuation of the ASDH under the same general anaesthetic.
Clinical profile of primary progressive aphasias in a tertiary care centre from India
Published in International Journal of Speech-Language Pathology, 2019
Appaswamy Thirumal Prabhakar, Vivek Mathew, Ajith Sivadasan, Sanjith Aaron, Anirudh George, Mathew Alexander
Of the 23 patients with PPA, 16 (69.6%) were diagnosed with PPA-G. The mean age was 58.8 years and more males were affected. The mean duration of disease at the time of presentation was 3 years. Patients presented with agrammatism, anomia and non-fluent speech. Their speech was effortful and agrammatic, and single word comprehension was normal but complex comprehension was impaired. Phonemic paraphasias were noted in five patients. Two patients had severe apraxia of speech (AOS) at the time of presentation. Seven patients were bilingual, and 3 patients had relative preservation of the mother tongue. During the follow-up period, 3 patients developed features of cortico-basal syndrome and parkinsonism. MRIs of the brains of patients showed prominence of the left Sylvian fissure in 15 (93.7%) patients and left inferior frontal gyrus atrophy in 12(75%) patients.
Beyond descriptive neurology: Broca, cerebral hemodynamics, and cortical function
Published in Journal of the History of the Neurosciences, 2018
Broca’s understanding of the potential of the collateral circulation in cerebral ischemia was as sophisticated as ours is today. Contemporary neurologists, who can assemble arteriography, computed tomography, magnetic resonance imaging, and positron emission tomography as aids in the diagnosis and treatment of stroke, are sometimes surprised that the concepts on which they rely were known to their nineteenth-century predecessors. Chief among them is the ability of the ischemic area to recruit blood from unaffected arteries. Most strokes involve the distribution of the middle cerebral artery, which includes the frontal, parietal, and temporal lobes about the Sylvian fissure. The central core of a stroke is irrevocably destined for infarction, whether the occlusion is at the origin of the internal carotid artery or more distally within the main trunk of the middle cerebral artery. The periphery of a stroke, referred to as the penumbra (Hakim, 1987), may only be ischemic and may remain viable if it is revascularized. This can occur if anastomoses develop to supply the penumbra across a border zone region. Therefore, blood flow across the border zones is a major determinant in the extent and severity of a stroke. The capacity to form anastomoses to revascularize the penumbra depends on three factors: the integrity of the circle of Willis, through which the major cerebral arteries communicate at the base of the brain; the size of the anterior and posterior communicating arteries and extent to which they are free of arteriosclerosis; and the speed at which the occlusion of the affected artery occurs, that is, rapidly with embolization, slowly with thrombosis.
Related Knowledge Centers
- Cerebral Hemisphere
- Inferior Frontal Gyrus
- Insular Cortex
- Neuroanatomy
- Parietal Lobe
- Transverse Temporal Gyrus
- Frontal Lobe
- Temporal Lobe
- Brain
- Sulcus