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Lateralization of Hemispheric Function – Motor Control and Sense of Self
Transcript of Lateralization of Hemispheric Function – Motor Control and Sense of Self
Dynamics of hemispheric specialization and integration in the context of motor control
Two fundamental principles
Left and Right
for motor control:
task-related charecteristics of activity:
functional specialization of neural regions
functional integration between neural regions
with respect to motor processes lateralization is
dynamic and time-dependent
dependent on task and performer
it is inter-regional interactions of functionally specialized regions that
enables coherent behavior
Broca & Wernicke
John Hugh Jackson
lateralization of motor function in the LH
Is the RH involved in motor control?
conflicting movements (anti-phase vs. in-phase)
spatial tasks (e.g. orientation, grasping...)
exploratory tasks: novel and unexplored actions
regulation of limb posture and position, target allocation
adaptive behavior in a changing
direction of attention
complex movements: control of limb trajectories
no matter whether one or both hands, similar or different movements
experience-based planning of actions
learning and recovery of skilled behaviour
internal representation for sequential actions
LH: sequential planning based on internal representations of previous experience
RH: adaptation to novel sensory situations
LH: motor complexity, unimanual or bimanual
RH: final position specification, conflict situation
and Sense of Self
Left Hemisphere Dominance
a) significant differences in MRI signal intensity
Right Hemisphere Dominance
Relative regional cerebral blood flow increase and extent related to conflicting visual feedback
bimanual coordination task with anti-phase versus in-phase movements
Left and Right Hemisphere Dynamics during Motor Learning
right superior parietal cortex (1), right dorsal premotor cortex (2), right dorsolateral PFC (3), right ventral premotor cortex (4) and left cerebellar lobule VI (5)
left dorsal premotor cortex (1), bilateral M1 (2), cingulate motor cortex (3), putamen/ globus pallidus (4), cerebellum dentate nuclei (5) and superior temporal gyrus (6)
regions of neural activity decrease (a) and increase (b) during learning of bimanual coordination involving complex spatiotemporal relationships between the limbs
shift from predominant right- to left-hemispheric activity
suggests a specific monitoring role of the RH in conflict situations with spatial task demands
increase in activity in the right dorsolateral PFC
b) relative regional cerebral blood flow increase and extent
predominant role of LH in motor tasks involving complex movements and attention
How does dynamic integration work?
What happens in the case of a lesion of one hemisphere?
Is this a localization hypothesis?
As a clarification: The talk is not about localization, but about functional specialization.
Of course there is no clear boundary between tasks that the left hemisphere, or the right hemisphere, exclusively perform on its own.
Rather the central idea is that the hemispheres are specialized, in the sense that a predominant activity can be measured in one or the other hemisphere dependent on the properties of performer and task.
The Somatic Marker Hypothesis
emotion influences cognitive decision-making
amygdala, brain stem nuclei
insula, somatosensory cortices
Antonio Damasio: A Hierarchical Model of Self
= neural representations of the body interior,
which serve as reference for all other representations
Three Levels of Self
The Autobiographical Self
forms the conscious mind
can be in states of rest
not consciously accessible
facts can gain different significance
contents and events get a different emotional weight
self is constituted as experiences are consolidated, modified and re-constructed in memory
main contribution to the consolidation of memories, also in dreams
save single autobiographical objects + make them conscious in impulses
coordination across the brain:
retrieve specific objects as images
pass images to the proto-self
save patterns of impulses associated to the object
Mechanisms of the Autobiographical Self
organisation depends on significance and order of experiences
= stable singular reference point, the "I" and "me"
associative nuclei of the thalamus
claustrum: neuroanatomical connections to sensory areas
superior and medial temporal lobe
medial prefrontal cortex (mPFC)
tempero-parietal junction (TPJ)
postero-medial cortices (PMC)
highly connective cortical regions, such as:
re-activate sensory regions
regions in midbrain and brain-stem involved in processes of the core-self
Neural Structures and Mechanisms
convergence-divergence regions: many cortical interconnections
the PMC has a special role in the constitution of the autobiographical self
Evidence for the Role of PMCs in Self-Constitution
coma, vegetative states
very effective in PMC
less regional blood flow
activity decreases from wake state to REM to deep sleep
increase in metabolism in case of improvement/recovery
circumscribed lesions lead to disruption of conscious states
PET, fMRI: PMC is the region metabolically most active
interoceptive info from inner organs
propriorecepetive and kinesthetic afferentes from muscles
exteroreceptive info from the world
use biological markers
PMC is a hub within the brain
reciprocal connectivity to important higher-level cortical areas:
–> attention and reward
–> motor planning
(somato-)sensory association areas
–> multimodal integration
+ basal ganglia
–> motor execution
PMC coordinates cortical with subcortical activity
maps current state of the organism
reaction to the environment
representations of organism with respect to the environment
extended autobiographical self-perception requiring memory and reason
Our biography is constantly updated by intero-, exteroceptive and skeleto-muscular information.
This involves a variety of different brain structures from brain stem to subcortical nuclei and higher cortical areas, associated to varying degrees of self-awareness.
The autobiographical self relies on the convergence-divergence architecture, particularly
Right Hemisphere – Emotional and Corporal Self
Left Hemisphere – Reflective Self
right parietal lesions impair body image
can lead to left-sided neglect, anosognosia, anosodiaphoria
Devinsky, O. (2000). Right Cerebral Hemisphere Dominance for a Sense of Corporeal and Emotional Self. Epilepsy & Behavior, 1(1), 60–73.
Damasio, A. (2010). The Autobiographical Self. In Self Comes to Mind: Constructing the Conscious Brain. New York: Pantheon Book.
sense of ownership + agency
RH is essential for an individual's awareness of his own corporal being and his relation to the environment
right parieto-temporal lesions impair topographic orientation
right frontoparietal lesions affect sense for familiar/unfamiliar things and can lead to experiential phenomena, e.g. fear, mania
right frontal lesions impair the relation of self to the social world, hence social perception and behaviour
"The left hemispheric linguistic and praxis self, which is defined by verbal thought and skilled movements, appears to be complemented by a more basic self, both corporeal and emotional, that lies largely within the right hemisphere."(p.61)
LH is language-dominant and essential for conscious thought, self-reflection and fine-skilled movement
"integrator system" of unified consciousness
established classical view: the LH is constitutive for the self
recent lesion studies reveal important functions of the RH:
links sequence of experiences into a unified (verbal) narrative
reflective consciousness, self-awareness, meta-cognition
introceptive verbal reports
verbal behavioural plans, intentional behaviour
association of immediate environmental information to objects of memory
and future self
formation and recall of memory
region on the midline of the brain
coordinates activity of other CD-regions
Ngan-Tram Ho Dac
University of Osnabrueck
Summer Term 2013
The Neuroscience of Self
Volitional Action and Self-Regulation
– Neurobiological Mechanisms
The findings that specific cognitive functions are impaired when one hemisphere is damaged does not necessarily contradict the thesis put forward by the authors.
There is also contrary research, showing that one hemisphere can take over the function of the other, in patients with unilateral cerebral lesion.
To repeat again: the authors suggest functional specialization that combines with hemispheric integration to give raise to adequate cognitive functioning; not exclusive localization of function.
Specific tasks require extensive and continuous interaction between both hemispheres and cannot be realized by either of them alone.
For instance, motor control in usual everyday situations relies on fine-grained and complex sequences of movements (LH), as well as on senso-motor coordination and spatial orientation (RH).
Efficient gating of information is suggested to be controlled by the corpus callosum and involves functional inhibition (e.g. unilateral actions) as well as facilitation (e.g. bimanual coordination tasks).
Can the self be localized in the brain at all?
How much can we conclude from pathological cases and lesion studies?
Which model seems more plausible to you,
Does distinguishing levels of self make sense?
Supplement: Damasio's Somatic Marker Hypothesis
This holistic view suggests that cognitive processes, such as decision-making, rely on somatic (or bodily) states. Accordingly, reflective and corporal states need to interact to produce coherent intentional behaviour.
Damasio's Model includes much more brain structures. Particularly, it accounts for the complex functional interactions between subcortical and cortical regions that give raise to different levels of self. It is much more detailed and extensive than a mere distinction between left and right hemispheric functions that respectively realize a reflective or a corporal self.
However, the models can also be combined. Specialized functions of right and left hemisphere have been shown in various studies and should not be denied. These might be mediated by the PMC.
The distinction makes sense, phylogenetically and ontogenetically. Animals and small children have a more basic sense of self, while children only develop an autobiographical self at the age of 7-8.
There are different tests for self-awareness, for instance, mirror and video self-recognition test, false belief test (ToM), etc.
These tests are passed at different levels of development.
Very similar distinctions can also be found in psychological memory models (Endel Tulving: separate episodic/autobiographical memory), as well as in philosophical self models (Dan Zahavi: minimal core self vs. Paul Riceour: Narrative Identity)
Lesions in specific regions lead to loss of specific types of self-awareness. Especially in the midbrain, a damage of the (dorsal) tectum leads to a lack of sensori-motor integration, while a lesion of the (ventral) tegmentum results in a loss of basic awareness.
However, it is difficult to conclude from single pathological cases or lesion studies to the functioning of the brain in a normal state. Usual activity might be much more complex and requiring wide-range interactions than can be studied from local loss of function.
In total, the search for a neural self constitutes a neuroreductionist view, which cannot provide a more holistic picture including social, psychological and phenomenological aspects of self (constitution).