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Lateralization of the Contents of Memory
Published in Robert Miller, Axonal Conduction Time and Human Cerebral Laterality, 2019
We have already seen hints that language might not be centred on the left hemisphere in a unitary fashion, when discussing American sign language. However, a role for the right hemisphere in some aspects of language has been known since the 1960s: Initially it became clear, from split-brain and hemispherectomy studies that the right hemisphere mediates important aspects of the visual recognition of words (Smith, 1966; Gazzaniga and Sperry, 1967; Gott, 1973; Levy and Trevarthan, 1977; Bergego et al., 1993). Such a function might be expected from what we have already discussed in terms of perception of complex stimuli. Subsequently, interest has grown in the differential lateralization of semantic as opposed to phonetic attributes of words. This also came initially from study of split-brain patients. For instance, Gazzaniga and Sperry (1967) found that the isolated right hemisphere was able to recognise individual words, both written or spoken (e.g. by pointing to a corresponding picture or object). However, occasionally substitutions were made between the correct word and a synonym (as though the meaning had been correctly identified rather than the word itself).
Roger Wolcott Sperry (1913–1994)
Published in Andrew P. Wickens, Key Thinkers in Neuroscience, 2018
Following WJ, many more split-brain patients would be tested. Almost without exception, the left hemisphere was found to be superior at understanding written language, and it excelled at solving analytical problems that required reason and logic. Despite this, the right hemisphere was not entirely without language since it could understand certain words and even read simple sentences. The right hemisphere was also better at solving spatial puzzles – and outperformed the left at recognising faces and pictures. Indeed, the right hemisphere (as demonstrated by the actions of the left hand) showed superior ability at drawing pictures, learning mazes and completing jigsaws.
Biological Dimensions of Difference
Published in Christopher J. Nicholls, Neurodevelopmental Disorders in Children and Adolescents, 2018
As the regions of the brain become more specialized, the connecting tracts specialize into those that are within the specific regions (association pathways), those that communicate across the connections between the left and right hemispheres of the brain (commissural pathways), and those that send messages to and receive input from the spinal cord (projection pathways). Usually, these connections all develop and work efficiently, although as we will learn, some developmental problems can occur because this doesn’t happen correctly. One example is something called “agenesis of the corpus callosum,” where the thick band of tracts connecting the left and right hemispheres of the brain don’t completely develop. The result is a developmental variation upon the concept of the “split brain,” research that has looked at how various cognitive functions are affected when the connecting pathways in adults were surgically cut to stop the spread of epilepsy. The Nobel Prize-winning work of Roger Sperry and his colleagues in the 1960s helped us to understand that the left and right hemispheres of the brain perform different kinds of cognitive activities and that severing the communication between the hemispheres results in a “disconnection” between these abilities (Nobelprize.org, 2003), much as might happen if the major bridges across the Mississippi River were all washed away.
Conscious intelligence is overrated: The normative unconscious and hypnosis
Published in American Journal of Clinical Hypnosis, 2022
Joel Weinberger, Mathew Brigante, Kevin Nissen
Theorists are hard pressed to find a place for consciousness in this model. They have come up with two propositions. One is a global workspace where many of the modules can meet and communicate. This one area of the mind/brain is therefore not modular (cf. Carruthers, 2006). The second solution is that what we term consciousness is really the action of yet another module. There are two versions of this latter hypothesis. One is based on Gazzaniga’s work on what has come to be called the split brain. He terms this module “the interpreter” (Gazzaniga, 1998, 1999, 2009). Its function is to note what we are doing, thinking, and feeling and make sense of it. The interpreter, like all other modules, operates outside of our awareness. What we experience is not some privileged access we can call consciousness. It is just another module operating unconsciously. The interpreter is not all-knowing. It does not always have access to the actual underpinnings of our experiences. When it does not have access to casual links, it will nonetheless fabricate a narrative that we experience as genuine. Sometimes these narratives make sense but sometimes they can be fantastic. As an example, Bisiach, Vallar, Perani, and Berti (1986) describe a woman who was hemiplegic and blind on her left side, due to parietal damage. She insisted that her left hand belonged to someone else.
Galileo’s Error: Foundations for a New Science of Consciousness
Published in Journal of the History of the Neurosciences, 2021
One wonders how Goff, with this notion of integrated system of particles, looks at clinical phenomena such as concussion, or unawareness of the ipsilesional side of space in patients suffering from visuospatial hemineglect, or the unawareness of a deficit like blindness (Anton’s syndrome) that are commonly associated with consciousness? And what about delirium, delusional states, and hallucinations? Goff does not deal with these clinical conditions, but he does discuss another remarkable phenomenon: consciousness in so-called split-brain patients. In fact, this is the only actual neuroscientific phenomenon Goff attends to in more detail. In the 1980s, the anecdote of a woman in whom the corpus callosum was split in order to control severe epileptic attacks triggered an intense dispute on consciousness. The woman reported that she would stand in front of the closet, considering what to wear, and her left hand would pick one piece of clothing and her right hand would reach for another. It seemed that each hemisphere had its own wishes, its own volition. It was argued that only the left hemisphere was able to talk about its wishes and explain its actions, whereas the right was able to perform reasonable action but simply could not communicate. What had happened to her consciousness? Did the surgery produce two consciousnesses, or did it split consciousness in two? Referring to the German panpsychist philosopher Luke Roelofs, Goff argues that what we see here is a “decombined” consciousness.
The effects of aerobic exercise on corpus callosum integrity: systematic review
Published in The Physician and Sportsmedicine, 2020
Paul D. Loprinzi, Jacob Harper, Toshikazu Ikuta
Integrity of the human CC is often measured via diffusion tensor imaging. Including metrics of fractional anisotropy (FA), higher values indicate greater white matter integrity. Also, calculated from axial diffusivity (AD) and radial diffusivity (RD), as well as mean diffusivity (MD), higher values indicate lesser white matter integrity. Integrity of animal (mice) CC often consists of anesthetizing the specimen to prepare brain tissue under investigation. Analysis is conducted through dissection followed by microscopic evaluation or custom-made MRI devices. Dissection of the CC has been known to result in ‘split-brain’ where two cerebral hemispheres minimally interact and exhibit independence from each other [2]. Interhemispheric connectivity provided by the CC is associated with cortical functions. For example, in the context of motor function, the CC influences bi-manual motor performance and may be involved in transferring inhibitory signals to the opposing hemisphere before and during motor execution [5,6]. Association between motor functions and interhemispheric motor fibers via the CC has been shown in adults and children [7,8]. With this in mind, maintaining the corpus callosum integrity is essential.