🎯 Objectives
The students would be familiarized with the role of higher order brain functioning 🧠⚡ in learning 📖, memory 💭 and amnesias 🚫💭.
📋 Brain Correlates
- Brain correlates of Learning and Memory 🧠💾, Amnesia 🚫💭, Verbal/Nonverbal memory 📚🎨
- Famous case of Amnesia, H.M. 👨⚕️
💭 Memory and Learning
Memory is one of the puzzles where biologists 🧬, physiologists 🔬, neurologists 👨⚕️ started working early on. Krech (1973) 👨🔬 spent a lifetime investigating memory and believes that memory is one of the most intriguing phenomena 🧠✨. There are many hypotheses and there are many frustrations for those working in this field 😤.
Lashley 🔬 was a pioneer in the area of locating engrams 💾 - basically he was a zoologist 🦁 trying to locate where memories are stored 📍.
🤔 Lashley's Frustration
"I sometimes feel, in reviewing the evidence on the localization of the memory trace, that the necessary conclusion is that learning is just not possible." 😤
— Lashley 1950 👨🔬
📖 Definitions
Memory: is defined as information stored in the brain because of sensory and other experience 🧠💾👁️👂 (Bridgeman 1992, p. 324 📚).
Learning: is the acquisition of new memories 📖✨.
However, where exactly is this happening and how? ❓ Is there a specific location 📍 or diffuse connection and locations 🔗?
🔬 Lashley's Two Principles
Lashley formulated two principles 📋:
- Principle of Equipotentiality ⚖️
- Principle of Mass Action 🌐
⚖️ Principle of Equipotentiality
Principle of Equipotentiality:
Lashley trained rats to run the maze 🐀🗺️. The animals learned to discriminate between the light and dark alleys ⚪⚫. They were rewarded for light alleys ✅ and punished for going into the dark alleys ❌.
Lesioning various parts of the brain 🧠⚠️, he found that disruption of learning took place after lesions of the visual cortex 👁️🧠❌. He reported that for retention of visual tasks Visual cortex is important 👁️✅.
"Various parts of cortex contribute to memory at least for complex behaviors. No one part is more or less specialized than other ⚖️"
Neurons within a given sensory area are capable of participating in memory formation 🧠💾 - all are equipotential in contributing to the retention of a task ⚖️✨. Memories are also discretely located within each sensory cortex 📍 (though diffusely spread in that area 🔄). There are also memories for the specialized sensory function 👁️👂🤚.
🌐 Principle of Mass Action
Principle of Mass Action:
Lashley's rats were trained on complex tasks utilizing information from various sensory modalities 🧠🔄, requiring:
- Visual cues 👁️
- Somato-sensory cues 🤚
- Kinesthetic cues 🦵
- Auditory cues 👂
- How do we learn 📖?
- How do we forget 🚫💭?
- How we remember friends 👥, their faces 😊, spellings of names 🔤 or generally, telephone numbers 📞?
- Why do older people remember events long past 👴⏰ better than immediate past?
- Where are our memories located 📍?
- Why do different areas store different part of the memory picture 🧩, how does it get integrated 🔄?
- One piece missing ❌, how the defect is covered, or compensated ✅?
There are many such questions 🤔:
After the learning had taken place, Lashley lesioned parts of the cortex 🧠⚠️ and found that the greater the extent of the lesion, the greater the deficits in memory 📊❌. Retention is related to the size of the cortical areas removed 📏.
Thus, it appeared that cortical area is not important only the extent of damage ⚠️📊. Therefore, cortex works as a whole 🌐, the more cortex involved in learning the better it is 📈✅.
👨 Application to Humans
- Short-Term Memory (STM) ⏱️
- Long-Term Memory (LTM) 💾
Memories are retained in the STM (stored temporarily) ⏱️ when the physiological changes to store in the long-term memory are taking place 🧠⚡. The STM memories are transferred to LTM 🔄➡️💾.
Short-term memory ⏱️ → repeated thinking and reviewing 🔄 → Long-term memory 💾
🧠 Hebb - Pioneer of Memory Theory
Hebb 👨🔬 one of the pioneers of neurosciences and of memory research stated that memories remain in STM temporarily ⏱️. The reverberating neural activity 🔄⚡ (neural activity, which goes round and round and produces structural changes in synapses 🧠🔧) leads to LTM storage 💾.
Thus, the changes in neuronal biochemical structure 🧪 are the basis of LTM storage 💾.
He proposed a Two-stage memory theory ✌️💭 which is supported by everyday evidence 😊 that unless you keep repeating a telephone number 📞🔄 it becomes difficult to recall it ❌!
It is possible to learn with one sensory mode and use what is learnt and retained, in another mode 🔄. For example, the visual scanning of mazes 👁️🗺️ takes place, then one can go through it using the kinesthetic mode 🤚.
Humans and higher primates can do that easily 👨🦍✅ but lower animals cannot transfer information from one modality to another 🐀❌.
If memories were diffusely stored 🔄 then lower animals should also be able to do the same
🧠 Hebb - Pioneer of Memory Theory
Hebb 👨🔬 was a pioneer in proposing that memories remain in STM temporarily ⏱️. At the time reverberating neural activity 🔄⚡ goes round and round and produces structural synaptic changes 🧠🔧 and this leads to the LTM storage 💾.
The changes in the neuronal biochemical structure 🧪 is the basis of the LTM storage 💾.
Two-stage memory theory ✌️💭 is supported in everyday life 😊. Unless you keep repeating a telephone number 📞🔄 it is difficult to recall it ❌.
🔄 Cross Modal Transfer
Cross Modal Transfer: It is possible to learn something in one sensory modality 👁️ and use the information retained in another mode 👂.
iesa) There is no adequate method to identify where memories are stored 🚫📍, where memories are stored is not known effectively even after so many years of research 🔬📆.
b) Performance not memory may be affected 🏃❌💭 (if you remember there was a famous joke 😄: that if you cut frog legs 🐸🦵, the frogs forget to hop across lines 🐸❌--- performance not memory was affected by cutting the legs 🦵✂️)
c) How do we know that connections of other areas are not damaged by lesions to one area 🧠⚠️🔗? Lesion in one area may alter connection in other 🔄.
d) Lastly, is what we assess if the loss of memory or the loss of retrieval of memorystrong> 🚫📍. It is not known effectively after years of research 🔬.
b) Performance is not memory 🏃❌💭. This is affected by many things (famous joke ): cut the frog legs, the frog forgot how to hop 🐸🦵❌. No, it's not memory loss 🚫💭 but performance ❌.
and MemoryResearches using single cell recordings 🔬 have shown that learning changes single cells 🧬✨. There are:
- Measured increases in calcium ⚡📈 in neurons
- Decreases in potassium ⚡📉 flow
- Increases in number of certain synaptic receptors 📊
- Changes in RNA and proteins 🧬🧪
Impaired learning may be due to the deficits in biochemistry📈
RNA: These are the memory code molecules 🧬💾.
There are qualitative and quantitative changes in measures of RNA and protein synthesis 🧪 in animals, which have learnt a task 📖✅.
Heredity is memory passed on from one to another generation 👨👩👧👦🔄. The DNA is the template for RNA 📋, which determines the structure of proteins 🧪.
🐀 Hyden and Colleagues (1962)
Hyden and Colleagues (1962) 👨🔬 trained rats to walk on a tight rope 🐀🎪 as compared to normal rats 🐀. There was increase in RNA in brain cell nuclei 🧬📈.
🧪 Glassman and Colleagues (1974)
Glassman and colleagues (1974) 👨🔬 showed that changes in RNA and proteins were found after learning a shock avoidance task ⚡📖. Shock avoidance where the rats had to jump onto a platform at the sound of a buzzer 🦘🔊, whereas the controls had a buzzer but no shock 🚫⚡ and/or no platform to jump 🚫.
These rats were injected with labeled Uri dine 💉 (precursor for RNA 🧬), or labeled lysine 💉 (precursor for protein 🧪), 30 minutes before the experiment ⏰.
The amount of Uri dines incorporation decreased with time 📉 i.e. RNA synthesis decreased after training 🧬📉 and lysine increased after training 📈. RNA coding for new protein 🧪✨.
Labeled Lysine injected carried into cortex and hippocampus with acquisition 💉e task ⚡❌. Rats had to jump off a platform 🦘 when they heard a sound of a buzzer 🔊 whereas control rats heard the buzzer 🔊 but had no shock ⚡ and no platform 🚫.
They injected labeled Uri dine 💉 (RNA precursor) or labeled lysine 💉 (protein precursor) 30 minutes before the experiment 🧪.
Uri dines incorporation decreased over time 📉 (RNA synthesis decreased after training 🧬📉), lysine increased after training 📈 (RNA was coding for new protein 🧪✨).
Interesting experiments 🔬 have also been carried out where rats 🐀, chicks 🐥 and other species were trained and learnt a task 📖✅, these animals were decapitated and their brains homogenized and injected into the normal rats 💀🧠🔄💉.It was found that the injected animals learnt faster than untrained or un-injected rats 📈⚡
🧠 Brain Homogenate Experiments
Protein Synthesis:
Researches on single cell basis of learning have indicated evidence that Protein's synthesis is a necessary step in long-term memory 💾🔬. Protein's synthesis modifies characteristics and properties of neurons 🧠🔧.
Drugs that inhibit protein synthesis impair LTM storage but not STM 💊💾❌⏱️✅. The increased inhibition leads to increased deficits in learning 📊❌ (Bennet et al, 1977 👨🔬).
Azinomycin blocks protein synthesis 💊 blocked rats memory of location of the shock ⚡📍❌ but not the memory of location of food 🍽️📍✅!
Other important bio-chemicals are: Cyclic Amp 🧪, ACTH 💊, Vasopressin 💧, Acetylcholine 🧠 andp>
Drugs 💊 which inhibit protein synthesis also impair LTM 💾❌ but not STM ⏱️✅. The increased inhibition leads to increased deficits 📊❌ (Bennet et al. 1977 👨🔬).
Azinomycin 💊 blocks protein. It blocked rats memory for the location where they received shocks ⚡📍❌ but not the location of where there is food 🍽️📍✅.
Other bio-chemicals involved: Cyclic Amp 🧪, ACTH 💊, Vasopressin 💧, ACh 🧠, NE ⚡
Stress 😰 interferes with learning and retrieval of information 📖❌. We all are familiar with Blockade before important paper 📄⚠️!
Electroconvulsive therapy blocks protein synthesis ⚡🧪❌
🔄 Hebb's Consolidation Theory
Hebb's consolidation theory 🧠💭: Time required for STM to LTM ⏰⏱️➡️💾 any interference with consolidation would result in disruption of long-term recall ⚠️💾❌.
If there is a head injury then memory of events prior to injury lost 🤕📉 (retrograde amnesia 🚫💭), destroyed as evidence indicates that a small reminder brings back memories 💡✅.
In head trauma memory returns after delay or under tranquilizers 🤕⏰💊.
ECT affects both long term and short-term memories ⚡💾⏱️: Kalat (1980) 👨🔬 "ECT interferes with memories that are active at the time of ECS regardless of the fact whether formed recently or long ago" 📚
ECT ⚡ affects both LTM 💾 and STM ⏱️. Kalat 1980 👨🔬 "ECT interferes with memories that are active at the time of ECS ⚡⚠️ regardless of whether they were formed recently or long ago" 📚.
🧠 Plasticity and the Nervous System
Experiments by Hubel and weasel 👨🔬 have shown that anatomical changes take place in the visual cortex with experiences 👁️🧠📊.
👓 Horizontal Goggles Experiment
Horizontal goggles worn by kittens during early period of development 🐱👶👓 lead to firing of neurons when horizontal stripes are seen as adults ↔️🧠✨.
Similarly, if one eye receives more stimulation, the brain area for that eye is enlarged 👁️📈🧠 (more neurons respond 📊✅)
⚡ Shock to the Foreleg
Shock to the foreleg of young kittens ⚡🦵🐱 led to a greatly enlarged somato-sensory cortical area 🧠📈 (Increased stimulation led to increased areas for responding 📊✅).
🤚 Merzenich's Finger Experiments
Merzenich 👨🔬 carried out an experiment where he joined the third and index finger by sewing them together 🤞, the area for this "one" finger becomes large 📈🧠.
If the thumb is removed 👍❌ the areas for thumb in the cortex becomes smaller 📉🧠.
🎻 MRI Studies of Violinists
MRI's studies of violinist's brains 🧠🔬🎻 showed that their cortical auditory areas were enlarged as compared to normal 📈🧠📊.
⚡ Super Plasticity in Growing Brain?
There have been studies which have shown that an early start ⏰ e.g. for musicians 🎵, for language proficiency 🗣️, for players ⚽, for gymnasts 🤸, there is need to start early 👶✅. As the information, being sent to the sensory cortices when learning is taking place 🧠📖.
In language learning 🗣️, the left hemisphere growth spurt is recorded on EEG 🧠📈📊 between:
- 2-4 years of age 👶
- And another 12-15 years 👦
- Again only in the left hemisphere 🧠⬅️
There is increasing research in the early development and the neuronal stimulation 🧠⚡, nerve growth factor 🌱, and stem cell research 🧬🔬.
🚫💭 Amnesia
Amnesia is a memory disorder 💭❌, and patients suffering from Amnesia have been studied to find out more about how memory works 🔬.
👨 H.M.: The Famous Pure Amnesic
One of the most famous cases of amnesia is H.M: pure amnesic 👨🚫💭:
H.M. had severe epileptic seizures 🧠⚡ and for treatment of epilepsy, surgery was carried out when he was 27 years old 🏥👨. In addition, after the surgery he has been in the time freeze of being stuck at 27 ⏰❄️ (even 40 years later 👴)!
HM has amnesia for events prior to surgery, and has no LTM 🚫💭💾❌. He actually lives in the present, in STM ⏱️✅.
He has no IQ loss 🧠✅ as assessed by IQ tests 📋. He has been tested for memory using:
- The mirror drawing task 🪞✏️
- The digit span test 🔢
- Block tapping memory span test 🧱🤚
- Incomplete pictures test 🖼️
- Even eye blink Pavlovian type conditioning response 👁️🔔
He has damage in the temporal region 🧠⚠️ and this has provided evidence of the importance of temporal lobe (and hippocampus) in memory 🧠
🔄 Types of Amnesia
➡️ Amnesia
➡️ Anterograde Amnesia
• Anterograde: loss of ability to learn new information 📖❌. The amnesic can remember events before surgery or injury ✅. The complex perceptual motor learning abilities however are intact in these patients ✅.
Korsakoff's syndrome 🍺 is the severest form of Anterograde Amnesia, where damage is to the mammillary bodies and temporal lobe 🧠⚠️
⬅️ Retrograde Amnesia
• Retrograde: This form of amnesia is inability to remember event, which had occurred before brain damage ⏰❌🧠.
Confabulation is creation of pseudo memories to fill gaps 💭❓🔄.
🧠 Alzheimer's Disease
• Alzheimer's disease is one of the major diseases, which leads to severe memory loss 💭❌. This is the most common cause of dementia 🧠 (memory and intellectual impairment 📉).
Research 🔬 has provided evidence of Neurofibrils 🧠, amygdaloid plaques 🧠, neural degeneration 📉, also reduction in ACH 🧪❌ as the underlying pathology in Alzheimer's 🏥
🧠 What Studies on Amnesiacs Have Shown
1. Hippocampus 🧠 is not the location of LTM 💾📍❌ nor is it important for the retrieval of LTMs 🔍❌
1. Hippocampus is not the location of long-term memory 💾📍❌ nor is it important for retrieval of long-term memories 🔍❌
2. It is also not the location for immediate memories ⏱️📍❌
3. Hippocampus is involved in transforming STM to LTM ⏱️➡️💾✅
Studies have also shown the importance of mammillary bodies 🧠, and the Dorsomedial Thalamus 🧠 in memory 💭.
📚 References
- Carlson, N. R. (2005). Foundations of physiological psychology. Pearson Education New Zealand.
- Pinel, J. P. (2003). Biopsychology. (5th ed). Allyn & Bacon Singapore.
- Bloom, F., Nelson., & Lazerson. (2001), Behavioral Neuroscience: Brain, Mind and Behaviors. (3rd ed). Worth Publishers New York
- Bridgeman, B. (1988). The Biology of Behavior and Mind. John Wiley & Sons, New York
- Brown, T.S. & Wallace, P.S. (1980). Physiological Psychology. Academic Press, New York
- Bradshaw, J. L. & Mattingley, J. B. (1995). Clinical Neuropsychology: Behavioral and Brain Sciences. ACADEMIC PRESS
• Anterograde: loss of ability to learn new information 📖❌. The amnesic can remember events before surgery or injury ✅. The complex perceptual motor learning abilities however are intact in these patients ✅.
Korsakoff's syndrome 🍺 is the severest form of Anterograde Amnesia, where damage is to the mammillary bodies and temporal lobe 🧠⚠️
• Retrograde: This form of amnesia is inability to remember event, which had occurred before brain damage ⏰❌🧠.
Confabulation is creation of pseudo memories to fill gaps 💭❓🔄.
• Alzheimer's disease is one of the major diseases, which leads to severe memory loss 💭❌. This is the most common cause of dementia 🧠 (memory and intellectual impairment 📉).
Research 🔬 has provided evidence of Neurofibrils 🧠, amygdaloid plaques 🧠, neural degeneration 📉, also reduction in ACH 🧪❌ as the underlying pathology in Alzheimer's 🏥
🧠 What Studies on Amnesiacs Have Shown
1. Hippocampus 🧠 is not the location of LTM 💾📍❌ nor is it important for the retrieval of LTMs 🔍❌
1. Hippocampus is not the location of long-term memory 💾📍❌ nor is it important for retrieval of long-term memories 🔍❌ 2. It is also not the location for immediate memories ⏱️📍❌ 3. Hippocampus is involved in transforming STM to LTM ⏱️➡️💾✅ Studies have also shown the importance of mammillary bodies 🧠, and the Dorsomedial Thalamus 🧠 in memory 💭.📚 References