Higher functions of the nervous system

A physiological description of higher mental functions: Learning, memory, emotions and motivation

1. Higher Mental Functions Sufyan Akram MBBS PhD

2. Functions of specific cortical areas The primary motor areas have direct connections with specific muscles for causing discrete muscle movements The primary sensory areas detect specific sensations-visual, auditory, or somatic-transmitted directly to the brain from peripheral sensory organs The secondary areas make sense out of the signals in the primary areas

3. Functions of specific cortical areas Association areas receive and analyse signals simultaneously from multiple regions of both the motor and sensory cortices, as well as from subcortical structures Important association areas include: (1 ) the parieto-occipitotemporal association area , ( 2) the prefrontal association area, and (3 ) the limbic association area

4. Association Areas

5. Higher Intellectual Functions of the Prefrontal Association Areas Several decades ago, before the advent of modern drugs for treating psychiatric conditions, it was found that some patients could receive significant relief from severe psychotic depression by severing the neuronal connections between the prefrontal areas of the brain and the remainder of the brain a procedure called prefrontal lobotomy

6. Relief from psychotic symptoms came at the expense of a person's personality and intellect This procedure was highly controversial and has now been abandoned! Loss of ability to solve complex problems, Unable to learn to do several parallel tasks at the same time Level of aggressiveness is decreased, in general, they lose ambition Social responses were often inappropriate for the occasion, often including loss of morals

7. Language

8. Role of Language in the Intellectual Functions A major share of our sensory experience is converted into its language equivalent before being stored in the memory areas of the brain and before being processed for other intellectual purposes… For instance, when we read a book, we do not store the visual images of the printed words but instead store the words themselves or their conveyed thoughts often in language form

9. Language Wernicke’s area for LANGUAGE COMPREHENSION (comprehension of written words, sounds, signs ) Wernicke’s aphasia – can speak, but makes no sense Says “chicken” when pictures of chairs or trees are shown Broca’s area for LANGUAGE EXPRESSION (speak/ write words) Broca’s aphasia - can comprehend, but cannot speak Can identify trees, chairs etc. but cannot speak out

10. This figure shows the pathway involved in hearing and speaking . ( 1) primary auditory area; (2) interpretation of the words in Wernicke's area; (3) determination, also in Wernicke's area, of the thoughts and the words to be spoken; (4) transmission of signals from Wernicke's area to Broca's area by way of the arcuate fasciculus; (5) activation of the skilled motor programs in Broca's area for control of word formation; and (6) motor cortex to control the speech muscles. This figure illustrates the comparable steps in reading and then speaking in response. The initial receptive area for the words is in the primary visual area rather than in the primary auditory area. Then the information passes through early stages of interpretation in the angular gyrus region and finally reaches its full level of recognition in Wernicke's area. From here, the sequence is the same as for speaking in response to the spoken word

11. Learning & Memory

12. Learning and Memory LEARNING : acquisition of new information or skills Learning is a modification of behavior which results from training, observation and experience MEMORY : retention of information, skills or thoughts Short term memory and Long term memory

13. ATTITUDE (Adult learning differs from childhood learning) REINFORCEMENT MOTIVATION (intrinsic & extrinsic) LEARNING Principles of learning

14. Principles of adult learning Adults are independent and self-directing They have accumulated a great deal of experience, which is a rich resource for learning They value learning that integrates with the demands of their everyday life They are more interested in immediate, problem- centred approaches than in subject-centred ones They are more motivated to learn by internal drives than by external ones

15. LEARNING Non-associative Associative Connections between two or more stimuli e.g. Conditioned Reflexes (Pavlov’s dogs )/ learning hands-on that fire is hot Habituation – reduced responses to repeated stimuli Sensitisation - increased response Habituation/sensitisation depends on how important it is e.g. a mother sleeps through loud noises but wakes up at her baby’s cry

16. Reinforcement and Punishment Reward Positive reinforcement (Example: gift, praise) Relief Negative reinforcement (Example: pain killer, mum’s nagging) Punishment Positive punishment (Example: spanking, scolding) Penalty Negative punishment (Example: traffic fine, marks deducted)

17. MEMORY Declarative/ Explicit Implicit/ Procedural/ Non- declaratrive / Reflexive Memory of learned skills e.g. riding a bicycle/ route to home Simple classical conditioning Stored in several areas including CEREBELLUM, BASAL NUCLEI, PONS Once learnt, they do not require a conscious effort of recall Memory of learned experiences such as facts or figures e.g. remember birthdays Short-term memory consolidated into long-term memory in HIPPOCAMPUS Long-term memory stored in various parts of the neocortex Amygdala add emotional colour to memories

18. Organization of Memory… Long-term Memory Declarative memory Procedural memory Episodic memory Semantic memory Sensory information Sensory memory Short-term memory * Specific events ** Factual knowledge *** Reflexive memory * ** *** Execute task and Forget e.g. remembering the grocery list

19. Encoding the memory… Not known HOW (? Repetition) How important it is to you also matters Short-term memory is stored in the frontal lobe but only temporarily (a few seconds to a few minutes) & the information needs to be consolidated into long-term memory because the space is limited Long-term memory resides in the HIPPOCAMPUS and lasts years/ lifetime

20. Long-term Potentiation Because of the property of PLASTICITY (ability to alter the anatomy and function in response to changes in its activity patterns ); new neurons and synapses are produced in the areas involved in memory LTP : repeated stimulation results in increased strength of that synaptic connection (increased number of EPSPs ) ... Memory improves with repetition…

21. Brain dysfunction by location

22. FRONTAL LOBE DAMAGE Generally, damage to the frontal lobes causes loss of the ability to solve problems and to plan and initiate actions. If the back part of the frontal lobe is damaged: weakness or paralysis can result. If the middle part is damaged: people may become apathetic, inattentive, and unmotivated. Their thinking becomes slow. If the middle back part of the left frontal lobe ( Broca area) is damaged, people may have difficulty expressing themselves in words-an impairment called Broca (expressive) aphasia .

23. FRONTAL LOBE DAMAGE If the front part is damaged, any of the following may result: Difficulty processing and retaining new information Reduced fluency of speech Apathy (lack of emotion, interest, and concern) Inattentiveness Delayed responses to questions A striking lack of inhibition, including socially inappropriate behaviour

24. PARIETAL LOBE DAMAGE Damage to the front part of the parietal lobe on one side causes numbness and impairs sensation on the opposite side of the body. If the middle part is damaged, people cannot tell the right from the left side (called right-left disorientation) and have problems with calculations and writing.

25. PARIETAL LOBE DAMAGE If the right parietal lobe is damaged: people may be unable to do simple skilled tasks, such as combing their hair or dressing-called apraxia. They may also have trouble understanding how objects relate to each other in space . If the right parietal lobe is suddenly damaged: people are usually confused. They may ignore the serious nature of their disorder or deny its existence. They may neglect the side of the body opposite the injury. Such people may be unable to dress themselves or to do other ordinary tasks.

26. Neglect syndrome – stroke in posterior region of right hemisphere. The patient has not completed the left hand side of the picture.

27. TEMPORAL LOBE DAMAGE In most people, part of the left temporal lobe controls language comprehension. If that part is damaged: memory for words can be drastically impaired, as can the ability to understand language-an impairment called Wernicke (receptive) aphasia . If seizures result from damage to part of the temporal lobe: people may not be able to control their feelings or to think clearly. They may smell bad odors that are not there (a type of hallucination). Occasionally, these seizures cause personality changes. People may have an overwhelming urge to write.

28. OCCIPITAL LOBE DAMAGE If both sides of the occipital lobe are damaged: people cannot see, even though the eyes themselves are functioning normally. This disorder is called cortical blindness. Some people with cortical blindness are unaware that they cannot see. If the back part of the occipital lobe is damaged: people have difficulty recognizing familiar objects and faces and accurately interpreting what they see. They are usually unaware of their problem and often make up descriptions of what they see (called confabulation ). This disorder is called Anton syndrome .

29. Recovery… Plasticity of the remaining cerebrum Plasticity (ability of an area of the brain to alter its function) of the cerebrum varies from person to person and is affected by age and general health. Plasticity is most prominent in the developing brain For example, if the dominant hemisphere language areas are severely damaged before age 8 yr , the opposite hemisphere can often assume near-normal language function. Redundancy Redundancy refers to the ability of more than one area of the brain to perform the same function.

30. Cerebral dysfunction syndromes

31. Agnosia Inability to identify an object using one or more of the senses. Agnosias are uncommon but may affect any sense. Visual agnosias : Prosopagnosia – inability to recognise faces Agnostic alexia – inability to read Colour agnosia – inability to retrieve colour information e.g. what colour are bananas Object agnosia – inability to name objects

32. Amnesia Partial or total inability to recall past experiences. It may result from traumatic brain injury, degeneration, metabolic disorders, seizures, or psychologic disturbances.

33. Amnesia Deficits in any of these steps in memory can cause amnesia: Registration (taking in new information) Encoding (forming associations, time stamps, and other processes necessary for retrieval) Retrieval Amnesia can be classified as follows: Retrograde : Amnesia for events before the causative event Anterograde : Inability to store new memories after the causative event Sense-specific : Amnesia for events processed by one sense- eg , an agnosia

34. Amnesia Tansient global amnesia is anterograde and usually retrograde amnesia that begins suddenly and lasts up to 24 h. The amnesia typically remits spontaneously but may recur .

35. Aphasia Language dysfunction that may involve impaired comprehension or expression of words or nonverbal equivalents of words. It results from dysfunction of the language centers in the cerebral cortex and basal ganglia or of the white matter pathways that connect them.

36. Apraxia Inability to execute purposeful, previously learned motor tasks, despite physical ability and willingness, as a result of brain damage . When this occurs in children it falls under the category of “developmental a praxia”. Ideomotor Apraxia: problem in the execution or imitation of simple gestures (e.g., wave goodbye ) . The problem occurs in converting a command to a behavior . Etiology is left hemisphere and often involves language areas as well.

37. Testing Cognitive skills Dominant hemisphere disorders Listen to language pattern Hesitant Expressive dysphasia Fluent but does not understand spoken commands (e.g. hold up both arms) Receptive dysphasia Ask the patient to name objects Can’t Nominal dysphasia Does the patient read correctly? Can’t Dyslexia Does the patient write correctly? Can’t Dysgraphia Ask the patient to perform a numerical c alculation e.g. ask serial 7 test, where 7 is subtracted serially from 100 Dyscalculia Can the patient recognise objects? e.g. ask to select an object from a group Agnosia

38. Testing Cognitive skills Non-dominant hemisphere disorders Note patient’s ability to find his way around his home Can’t Geographical agnosia Can the patient dress himself? Can’t Dressing apraxia Note patient’s ability to copy a geometrical pattern e.g. ask patient to form a star with matches or copy a drawing of a cube Constructional apraxia

39. ; score > 24 normal; < 24 suggests dementia

40. In Summary… Cerebral function is extensively lateralized . Visual , tactile, and motor activities are directed predominantly by the contralateral hemisphere. Certain complex functions involve both hemispheres but are directed predominantly by one (cerebral dominance ) For example, the left hemisphere is typically dominant for language, and the right is dominant for spatial attention . Cerebral dysfunction may be focal or global. Diagnosis is mainly by clinical evaluation. Sometimes, neuropsychologic testing, and imaging may help. Left hemisphere is dominant in 95% right-handers and 60% left-handers!

41. Emotions & Motivation

42. The Limbic System The word "limbic" means ‘border’ Originally , the term "limbic" was used to describe the border structures around the basal regions of the cerebrum In modern neuroscience, the term limbic system has been expanded to mean the entire neuronal circuitry that controls emotional behaviour and motivational drives A major part of the limbic system is the hypothalamus , with its related structures

43. Emotions and Behaviour Emotion is a subjective, conscious experience characterized primarily by psychophysiological expressions, biological reactions, and mental states Emotion is a “positive or negative experience” that is associated with a particular pattern of physiological activity

44. Emotions and Behaviour Emotion is often associated and considered reciprocally influential with mood, temperament, personality, disposition, and motivation It also is influenced by hormones and neurotransmitters such as dopamine, noradrenaline, serotonin, oxytocin and GABA Emotion is often the driving force behind motivation

45. Emotions and Behaviour Emotion is also linked to behavioural tendency: Extroverted people are more likely to be social and express their emotions, while introverted people are more likely to be more socially withdrawn and conceal their emotions

46. Basic Emotions Some psychologists classify six emotions as basic: anger, disgust, fear, happiness, sadness and surprise More appropriately, it should be seen as a " wheel of emotions“ The complex emotions could arise from cultural conditioning or association combined with the basic emotions Alternatively , similar to the way primary colours combine, primary emotions could blend to form the full spectrum of human emotional experience

47. Emotions and Behaviour Feelings are subjective representation of emotions , unique to an individual Moods are diffuse affective states that generally last for much longer durations than emotions Affect is an encompassing term, used to describe the topics of emotion, feelings, and moods together

48. "Reward" and "Punishment" Function of the Limbic System Almost everything that we do is related in some way to reward and punishment If we are doing something that is rewarding, we continue to do it; if it is punishing, we cease to do it. Importance of Reward or Punishment in Learning and Memory- Habituation Versus Reinforcement Animal experiments have shown that a sensory experience that causes neither reward nor punishment is hardly remembered at all.

49. Role in Pleasure It operates by influencing the endocrine system and the autonomic nervous system. It is highly interconnected with the nucleus accumbens , the brain's pleasure center, which plays a role in sexual arousal and the addiction to recreational drugs… These responses are heavily modulated by dopaminergic projections from the limbic system

50. Motivation Impulse that drives our actions Physiological changes/ pleasure derived from stimulation of “pleasure centres” which activate dopaminergic neurones Avoidance associated with lateral portion of posterior hypothalamus & dorsal midbrain- punishment/ avoidance system

51. Specific Functions of Other Parts of the Limbic System Hippocampus is important in Learning Amygdala receives neuronal signals from all portions of the limbic cortex, as well as from the neocortex of the temporal, parietal, and occipital lobes-especially from the auditory and visual association areas Because of these multiple connections, the amygdala has been called the "window" through which the limbic system sees the place of the person in the world Limbic Cortex is the most poorly understood portion of the limbic system This cortex functions as a transitional zone through which signals are transmitted from the remainder of the brain cortex into the limbic system

52. In Summary… Limbic System is involved in motivation, emotion, learning, and memory Limbic system is where the subcortical structures meet the cerebral cortex It operates by influencing the endocrine system and the autonomic nervous system It is also highly interconnected with the nucleus accumbens , the brain's pleasure center

53. References Guyton and Hall Textbook of Medical Physiology , 12 th edition, 2011 Naish Medical Sciences , 1 st edition , 2011 Merck Manuals http:// www.merckmanuals.com/professional/neurologic-disorders/function-and-dysfunction-of-the-cerebral-lobes/

54. Thank you for your attention