2.2 To understand how language, memory and emotion are processed in the brain Flashcards
Localization of language
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Brain imaging: show that a large network in the temporal, parietal, and frontal lobes, including both hemispheres, contribute to language.
Anatomical areas associated with language
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- Figure A: inferior forntal gyrus and the superior temporal gyrus, in which Broca’s area and Werkincke’s area are located. It also includes the ventral parts of the precentral and postcentral gyri, the supramarginal gyrus, the angular gyrus and the medial temporal gyrus.
- Figure C: Heschl’s gyrus (primary auditory cortex) and parts of the superior temporal gyrus referred to as the anterior and posterior superior temporal planes (aSTP and pSTP). Together, Heschl’s gyrus, aSTP, and pSTP constitute the planum temporale
Other regions taking part in language
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- Supplementary motor area: responsible for the rhythmic mouth movements that articulate sounds
- Parts of the thalamus, dorsolateral parts of the caudate nucleus, and the cerebellum
- Visual areas (for reading), sensory pathways, and motor pathways
- Pathways connecting all of these various regions.
Werknicke-Geschwind model
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A model that proposes that comprehension is extracted from sounds in Wernicke’s area and passed over the arcuate fasciculus pathway to Broca’s area to be articulated as speech. Other language functions access this comprehension-speech pathway as well.
Fedorenko and Thompson-Schill model
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The temporal and frontal cortices connected by dorsal and ventral language pathways = extensions of the dorsal and ventral visual streams.
Information form body-sense regions of the parietal cortex also contributes to the dorsal and ventral language pathways and likely contributes to toch language such as Braille.
Fedorenko and Thompson-Schill model
Ventral language pathways:
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Transform sound (phonological) information into meaning (semantic) information, this is more of a top-down process, as it occurs when meaning is given.
Fedorenko and Thompson-Schill Model
Syntax
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Both pathways are involved in syntax (zinsleer), the dorsal pahtway categorises sounds into frequency of association and the ventral pathway extracts meaning from the grammatical organisation of words.
Both pathways are also involved in short- and long-term memory for the phonetic and semantic components of speech and in non-verbal speech.
Damage to the ventral pathways:
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Can cause one to still be able to read, but not be able the understand what it means.
Damage to the dorsal pathway
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Can make one unable to articulate, but can understand words.
Damage to both pathways
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Can make one unable to repeat words or attribute meaning to words.
Speech zones mapped by brain stimulation and surgical lesions: positive effects of cortical stimulation:
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Cortical stimulation produces: either positive effects, eliciting vocalisation that is not speech but rather a sustained or interrupted vowel cry, such as “oh”
Speech Zones Mapped by Brain Stimulation and Surgical Lesions: negative effects of cortical stimulaton
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Or it produces negative effects, inhibiting the ability to vocalise or to use words properly, including a variety of aphasia errors:
- Total speech arrest or an inability to vocalise spontaneousely
- Hestitaion and slurred speech: door: stimulation of the dorsal regions in Broca’s area and the ventral facial regions of premotor and motor cortex.
- Distortion and repitition of words and syllables: these effects primarily result from stimulating Broca’s and Wernicke’s areas and also the face area.
- Number confusion while counting: pat may jump from “6” to “19”, resulting from stimulation of Broca’s or Wernicke’s.
- Inability to name objects despite retained ability to speak: arise from stimulation throughout (anterior)Broca’s and (posterior)Wernicke’s speech zones.
- Misnaming and perseverating: occurs during both Broca’s and Wernicke’s speech zones (anterior and posterior)
Speech zones mapped by TMS
Transcranial magnetic stimulation (TMS)
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With TMS, connections between brain areas and specific brain regions can be mapped. The stimulation does not easily access regions located deep within sulci.
Speech zones mapped by TMS
Anterior regions of Broca’s is implicated in:
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Semantic processing (processing the meaning of words)
Speech zones mapped by TMS
Posterior region of Broca’s area is implicated in:
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Phonological processing (production of words)
Speech zones mapped by brain-imaging
Which widespread brain regions do words activate?
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- Occipital lobe
- Parietal lobe
- Temporal lobe
- Frontal lobe
- Thalamus
- Cerebellum
Speech zones mapped by brain-imaging
Using PET: more specific fucntions for some language areas became clear:
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- No overlap occured in visual and auditory activation during the passive task, implying that processing word forms in the two modalities is completely independent.
- During the speaking tasks, bilateral activation occured in the motor and sensory facial areas and the supplementary speech area as well as activation of the right cerebellum.
- Generating verbs activates the frontal lobe. especially the left inferior region, including Broca’s area.
- The verb-generation task also activated the posterior temporal cortex, anterior cingulate cortex, and cerebellum.
Wernicke’s area
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Mainly for analysing auditory input
Broca’s area
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Displays speech moevemtns and is involved in syntax and memory.
Neural networks for language
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Many models are based on the idea that language is widely distributed in cortical and other brain structures.
There are 2 language-network models that illustrate the distribution in the cortex:
1. Core language network (Fedorenko and Thompson-Schill)
2. Nodes and neural webs for language (Salmelin&Kujala)
Neural networks of language
Core language network (Fedorenko and Thompson-Schill)
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- network of 5 functional modules (hearing, converting sound to meaning, articulating language).
- Each module= multiple nodes (the circles) that likely serve a common function.
- node= active in producing phonemes, representing animal words, representing word actions and so on.
-advantage: allows to see at a glance the distribution of language across the left hemisphere, and to see that different parts of the network serve different functions.
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Neural networks of language
Nodes and Neural Webs for Language (Salmelin&Kujala)
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Meaning comes through the connections between nodes proposed to comprise neural webs.
Nodes can be single cells or collections of cells, and a web consists of nodes and their two-way connections.
The nodes and their connections can be local or widely distributed across the cortex.
- if a word contains visual content, the web contains visual areas. Language is thus widely distributed across the cortex.
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Unconscious inference
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Is a process outside awareness and learned by experience, whereby observers use knowledge to perceive and make decisions.
Emotion
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Is the cognitive interpretation of subjective feelings.
Neuroosychologists view it as an inferred behavioural state called affect, which is a conscious, subjective feeling about a simtulus, independent of where or what it is.
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Components of emotion
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The experience of emotion has 4 principal behavioural components, and each can be quantified as well as observed:
1. Psychophysiology
2. Distinctive motor behaviour
3. Self-reported cognition
4. Uncoscious behaviour
Components of emotion
Psychophysiology
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- Includes central and automatic nervous system actibity and the resulting changes in neurohormonal and visceral (somatic) activity.
- Emotion changes things such as heart rate, blood pressure, distribution of blood flow and perspiration
Components of emotion
Distinctive motor behaviour
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Facial expression, voice tone and posture are all emotional states, motor behaviours are important when observing emotions as they convey overt action that may differ from observed verbal behaviour.
Components of emotion
Self-reported cognition
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Cognitive processess are derived from self-reports. It works with subjective emotional feelings (feeling of love or hate) and other cognitive processes (plans, memories, ideas)
Components of emotion
Unconscious behaviour
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This component incorperates unconscious inference - cognitive processes of which we are not aware that influence behaviour. We may make decisions on the basis of “intuition”.
Historical views
Investigating the anatomy of emotion
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Lesion and studies on the diencephalon led to the idea that the thalamus and hypothalamus contain the neural circuits for the overt expression of emotion and for automatic responses such as changes in blood pressure, heart rate etc.
The cortex was envisioned as inhibiting the thalamus and hypothalamus. The thalamus was seen as activating the cortex during autonomic arousal, presumably to help direct the emotion to the appropriate stimulus.
Papez’s theory of emotion in brain
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First major theory in the neurology of emotion.
The structure of the limbic lobe forms the anatomical basis of emotion, and the limbic structures act on the hypothalamus to produce emotional states.
The neocortex played no part in producing emotional behaviour, but Papez believed the cortex was necessary for transforming events produced by limbic structures into our experience of emotion.
Theory of 1937, ze begrepen toen nog niet alle brein regio’s dus is nu niet meer relevant.
Klüver-Bucy syndrome
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Has been observed in people with a variety of neurological diseases.
A lack of affect is prominent and can have following symptoms:
- Tameness and a loss of fear
- Indiscriminate dietary behaviour: willingness to eat many types of previously rejected foods
- Grealty increased autoerotic, homosexual, and heterosexual activity, with inappropriate object choice
- Hypermetamorphosis, a tendency to attend and react to every visual stimuli
- A tendency to examine all objects by mouth
- Visual agnosia
Symptoms of Klüver-Bucy syndrome can result from:
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Meningoencephalitis= an inflammation of the brain and the meninges, and by bilateral removal of the amugdala and inferior temporal cortex.
This syndrome will not be seen if there’s only a removal of unilateral amygdalectomy.
Brain circuit of emotion
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Hippocampus, amygdala, and prefrontal cortex all connect with the hypothalamus.
The mammillary nucleus of the hypothalamus connects to the anterior thalamus –> which in turn connects to the cingulate cortex.
Connections form the cingulate cortex complete the circuit by connecting to the hippocampus, amygdala, and PFC.
Although the whole circuit is important to emotional behaviour, the PFC (especially the oribitofrontal and ventromedial regions) and amugdala hold the key to understanding the nature of emotional experience.
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Orbitofrontal cortex and emotion
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Is especially important in emotion because it represents positive and negative rewards and learns which previously neutral stimuli are associated with positive and negative rewards and when these associations change.
Pleasure is mostly represented by acitivity in the OFC, particularly in a mid-anterior subregion. The medial orbital region encodes subjective pleasure ratings, but it also monitor and predicts reward value.
3 principal subdivisions of amygdala
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- Corticomedial
- Basolateral
- Central areas
Cells of the amygdala
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Receive input from all sensory systems. The cells require complex stimuli such as faces.
The cells can respons to visual, auditory, somatic, gustatory, and olfactory stimuli.
The amygdala can therefore create complex image of the sensory world, and this image is especially sensitive to stimuli that might be threatening or dangerous.
How does system of amygdala work?
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System =rapid and reliable identification of affectively significant stimuli, both pleasant and unpleasant.
It is especially sensitive to stimuli that might be threatening or dangerous. So the amugdala plays a central role in attaching hedonic values to both emotional and other environmental stimuli.
Bilateral amygdala damage makes animals very tame and fearless, with a lack of emotional responsiveness.
Theories of emotion
Appraisal theories of emotion
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These theories argue that our emotions are extracted from our appraisal (waardering/inschatting) of internal and external events, which causes an affective response.
VB: if a poisonous snake is encountered, physiological changes arise, such as increased heart ratem respiration, and sweating, which is interpreted as fear.
Appraisal theories of emotion
Damasio’s somatic marker hypothesis
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When person is confronted with a stimulus of biological importance, the brain and the body changes as a result. The physiological changes in response to the poisonous snake would be called ‘somatic markers’.
- Emotions necessary to make rational decisions, when person faces risks or conflicts.
- People with reduced emotions show impairments in personal or social matters, especially when they include possible risk or conflict.
Theories of emotion
Cognitive-emotional interactions
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These theories argue that emotions are evolved to enhance an animal’s survival, and that the cognitive and emotional processes grew more interrelated as the brain evolved.
Cognitive-emotinal interactions
LeDoux
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Stated that all animals detect and respond to danger, and the related neural activities evolve to produce a feeling - fear.
Fear= an emotion that has decreased in humans as they evolved, rarely due to predation, but due to stress.
- Underlying neural system fear= similar in both conscious and unconscious
- Fear can be studies by fear conditioning.
LeDoux: amydala
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The key brain structure to develop conditioned fear. It stimulates hormone release and activates the autonomic nervous system, generating tge emotion of fear.
This can be measured in a physiological way, through heart rate or respiration, and quantitative ways, such as standing motionless (freeze) when stimulus is presented.
LeDoux: amygdala damage
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Interferes with fear conditioning.
The neurons in the amygdala have an evolutionary sensitivity to nega stimuli, such as nega facial expressions of others, which might indicate disapproval of a social group of the stimulus, or person.
The neural networks in the amygdala can also learn from experiences about dangerous stimuli.
LeDoux: hippocampal damage
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Interferes with the development of contextual fear associations.
The orbital and medial prefrontal regions have significant connections with the amygdala, suggesting that amygdala prefrontal circuits have a role in forming thoughts about fearful stimuli.
Cognitive asymmetry and emotion
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These theories follow the idea that related emotional systems must be lateralized.
Cognitive asymmetry and emotion
Left-hemisphere lesions
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Generate (het ontwikkelen van) extreme responses marked by intense fear and sadness.
- Lack of affect
- appearance of depression, especially after strokes that produce language difficulties.
- Talk less
- Decreased facial expression
Cognitive asymmetry and emotion
Right-hemisphere lesions
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Indifference
Talk more
Tone of voice, aprosodia is when the tone in speech is not present:
- Motor aprosodia: difficulty in generating emotional aspects of language, due to damage to Broca’s area in the right hemisphere
- Sensory aprosodia: not being able to interpret emotional aspects of language, due to damage to the area in the right hemisphere similar to Wernicke’s area
Interpreting emotional behaviour
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Humour (which contributes to personality and is important in social life) can not be understood by right frontal lobe patients.
Right also responsible for processing faces and facial expressions, while the left hemisphere may be responsible for understanding context.
Different facial expression can be processed in different areas of the brain.
VB: fearful expressions activate the amygdala and disgust expressions activate the insula.
Temporal lobe patients
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Temporal lobe pat’s show a clear personality change
- Right temporal lobe pat’s: observed to be more obsessional.
- Left temporal lobe pat’s: were preoccupied with ‘individual fate’.
