Deficit in memory for information learned before the onset of Amnesia, Impairment is often temporally graded, old memories are well preserved.
Hallmark feature of organic amnesia, failure to form new memories, Short delay leads to remember short prose piece, long delay leads to harder to remember, Short term memory is intact, significant forgetting, learning deficits occur for verbal and spatial
Reflects transfer from short term memory to long term memory
Reflects retention in Short term memory
Don't show primacy effect but have recency effect a.k.a. Remember words at the end of the list.
Case study of Amnesia, Surgical Removal of Hippocampus and Surrounding cortex, Severe new learning deficit (anterograde amnesia) Some loss of events 1-3 years prior to surgery (retrograde amnesia) Intact IQ, language, attention, knowledge base, childhood memories
Short Term Memory, working memory
Frontal and Temporal Lobes
Long Term Memory, semantic and episodic
Responsible for the formation of Long Term Memories leads to consolidations, important for relational memory
Damage to the thalamus and mammillary bodies, Retrograde and Anterograde amnesia and other symptoms due to thimone deficiency.
Herpes Simplex Encephalitis
Used to treat epilepsy, damage to temporal lobs
Damage to Hippocampus
Anterior Communication Artery Aneurysm
Damage to Basal Fore Brain
Animal Models of Amnesia
The neuro anatomy of the medial temporal lobe is similar in many mammals.
Delayed non-matched sample task
Task: pick opposite location relative to where reward was last seen so monkeys sees reward then screen down , reward
Declarative vs. Non Declarative
Medial temporal lobe, amnesics showed spared procedural learning and perceptual priming
Semantic vs. Episodic
Patient KC severe anterograde and retrograde amnesia partially for episodic and source memories. KC could learn some new semantic information
Type of memory retrieval in which the information to be retrieved must be pulled from memory with very few external cues
Recall has failed (tip of the tongue)
The ability to match
Semantic vs. Episodic
Hear a list of related words, asked to look at a list of test words, decide which ones you've seen and which ones you hadn't
Making an association between object information with spatial information
Three Layers of the Hippocampus
CA1 Pyramidal Cells, Granual Cells, CA3 Pyramidal Cells
Long Term Potentiation
response to stimulation over time will increase in the granule cells, post synaptic potential are graded
Neurons that fire together wire together
more than one input must be active simultaneously
Weak inputs are strengthened with the co-occur with stronger input
Only stimulated synapses are potentiated8
Gated by glutamate and Mg2, excited by MDA and glutamate, usually blocked by magnesium Ion, Weak stimulus don't cause it to open
Prevents currents from flowing through
inability to recognize the meaning of words
can't tell the differences between different worlds.
Storage of words and concepts, a mental store of information about words that includes semantic information ,Synaptic Information, Word forms. Like dictionary but no fixed content meaning words can be learned and more frequently used words can be accessed more quickly
Perceptual Analysis of linguistic input
speech comprehension and reading
Damage to Basal Fore Brain
Organization of Language
Sounds then Phonemes then Morphemes then Words then Sentences
Smallest unit of sound that makes a difference in meaning
Smallest meaningful unit in grammar
Concept, Lemma, Lexeme
Semantic Priming Effect
Facilitation of Word Recognition due to semantic associations
Reading target word out loud
Lexical Decision task
Is the target word a word or a non word
Wernicke's Aphasia Patients
Make semantic paraphrases e.g. horse instead of cow
Similar errors in reading
Progressive Semantic Dementia
Progressive damage to temporal lobs, impairment in conceptual systems
Category specific semantic Deficits
Deficits for Living things. vs. Non living thing. Production and comprehension following left temporal lobe.
Warington et. al.
Knowledge about different classes of things depends to varying degrees on visual vs. functional properties, computation model can account for apparent category specific deficits with property based account
Caramezza and Shelton
Linguistics materials in previous studies poorly controlled conceptual categories
Difficult Problem-Variability in signal: speech sounds vary as a function of context. Unlike written input, identification of word boundaries is different in spoken input
Cohort Model of Speech Comprehension
time dependent process, speech processing starts with the very first phoneme all words beginning with that phoneme then become activated, as more phonemes are processed, non-matching word reps are eliminated form the cohort until only one remains, model is too simplistic -also competition between words that don't match
Speech v. Non Speech Sounds
Speech sounds activate more than tone. Areas that activate more strongly to words and non0words are almost entirely lateralized to the left hemisphere
Pick Up Electric (EEG) or Magnetic (MEG)
Signals that stem from large populations of neurons
Not good at localization but good at temporal resolution difference in activities on a fine time scale. To derive a signal related to a particular event, need to average over many trials aligned on a particular event (called ERPs in EEG)
use EEG to detect current pattern characteristics of seizure activity, good temporal resolution
Any given pattern observed on the surface of the scalp can result from many possibly locations of underlying neural generators.
A single dipolar change simulates an active neuronal population inside and result in a distinct pattern of signals
Better at the inverse problems so better spatial resolution, Magnetic field not as distorted as electrical signal but best signal comes from sulci, where pyramidal neurons are orientated parallel to skull surface
Comparison of Methods,fMRI and EEG or MEG
fMRI is good at spatial resolution, PET isn't as good. EEG or MEG excellent temporal resolution
Left Occipital Temporal Cortex
Shows preferential responses to letter strings vs. other visual stimuli. If damaged, can suffer from alexia
Word recognition specific deficit
Patients can't read non-words but can read irregular words. Problem with grapheme-phomeme conversion
Patients read everything by regularizing pronunciation. Problems with the direct rout.
Semantics (word recognition)
Semantically incongruous words elicit a negative ERP wave of 400 ms after stimulus onset: N400 Wave. Observed for many different manipulations. Independent of modality language. Indicates that by 400ms afterwords onset the words.
Grammar; the system of rules by which worlds are combined into phrases and phrases into sentences
Proceeds even for meaningless sentences
Garden Path Model (Syntax)
Sentences are processed in a way to minimize the amount of time spent on a assignment of syntactic structures, sentences have a preferred interpretation which is determined by minimal attachment and late closure
Minimal Attachment (GPM)
Minimize the number of syntactic nodes to be computed
Late Closure (GPM)
Attempt to assign incoming words to syntactic phrase currently being computed
Garden Path Effect
an incorrect interpretation of a sentence due to an inappropriate synaptic parsing. The model is Modular-Syntactic processing is encapsulated: cannot be influenced by other sources of information except after it is completed.
activates more strongly to complex than single syntactic structure.
After lesions to brocas area or ant. STG produce short
Positive ERP wave 600 ms after syntactic violation, also observed in sentencess with the garden path affect
Tip of the Tongue Phenomena
Failure to retrieve phonological rep despite access to semantic rep
Deficit in naming (extreme version of TOT)
Brocas Area (speech production)
May be specific to phonological encoding but posterior Broca's also involved in articulation
Left Basal Temporal
Cortical stimulation produces speech arrest
Connects Brocas and Wericke areas together
Difficulty in speech production to problems in programming articulation or control over articulatory muscles, also agrammatism; syntactic processing impaired, damage to classical brocas area
Difficult in accessing semantic and phonological representations for spoken output, persistent with aphasics requires lesions in surrounding post. Temporal inferior parietal cortex.
Higher Level process, directing cognitive resources towards processing. Limited ability to process thing in our environment on a deep level, withdrawing resources.
Stimulus independent affects
Neural correlates of delaying attention without stimulus (expectation)
Exogenous/Automatic. Attention drawn to a something that stands out. Spot color
Endogenous. Focus on unopened flowed. Something ordinary in the picture.
Characteristics of Attention
Can be reflexive or voluntary, limited capacity, no eye movement or head turning required.
Covernt Visual Attention
Ability to direct attention to a given location without eye movements to this location. Don't' turn your head or eyes away but still notice something
Ability to selectively process only a subset of information
Speeds up processing and make it more accurate.
Spatial Attention in the Brain
ERPs during spatial cuing task. Attentional effect found 70-100ms after stimulus-PL component Modulates activity in retinotopic cortex. Upper part is more active.
"Spotlight" spatial attention
increased activity in regions of retinotopic cortex, that represents the attended location