the lesioned brain Flashcards
what is TMS
- transcranial magnetic stimulation
- a means of disrupting normal brain activity by introducing neural noise
how does TMS work
- uses principle of electromagnetic induction
- Faraday’s coil = principle of TMS
- magnetic field must change rapidly
- induces electric field in brain causing tissue current
why do TMS studies?
can see if brain region is critical for task
advantages of TMS
- transient
- reversible
- interference/virtual lesion
- control location and duration of stimulation
- establishes causal link
TMS example study - Knecht et al (2002)
- did TMS on 20 participants who were left or right dominant language authorisation
- when dominant hemisphere stimulated slower at word-picture matching task (interfering)
- when non-dominant hemisphere stimulated faster (dominant hemisphere has more resources)
why do a control task in TMS
as TMS coil is heavy and makes people apprehensive
what is TES
- transcranial electrical stimulation
- more of a modulation technique as electrical stimulation = low (1-2mA)
- use battery
- deliver current through 2 sponges - less focal than TMS
types of TES
- transcranial direct current stimulation (tDCS)
- transcranial random noise stimulation (tRNS)
- transcranial alternating current stimulation (tACS)
tDCS
current flows from anode to cathode
tACS
current flows from anode to cathode and back at preset frequency
TES when applied once vs repeatedly
applied once = not much behavioural change
applied repeatedly = changes in neuronal excitability - can lead to changes in brain wiring
anodal stimulation
- faciliation effects
- inhibits GABA
- excitation
cathodal stimulation
- inhibition effects
- inhibits glutamate
- inhibitory
tACS and syncronisation
- applied to brain rhythms already in brain (measured by EEG)
- can enhance certain brain frequencies
- causes phase locking of a large pool of neurons - increases of neural synchronisation
tACS - lucid dreams
Voss et al (2014)
- applied tACS for 2 mins in REM sleep
- if applied at gamma frequency induced lucid dreams
TMS and TES
- prominent effect on cognitive processes
- cause after effects on excitability
- alternative to drugs when combined with behavioural training
classical neuropsychology
what functions are disrupted by damage to region X
- more intuitive
neuropsychology
studying brain damaged patients to gain insight into the normal brain
cognitive neuropsychology
can a particular function be spared/impaired relative to another cognitive function?
- what the building blocks of cognition are regardless of where
which type of neuropsychology uses
- group
- and single case methods
classical = group cognitive = single
types of strokes
ischemia - clot
hemorrhage - bleeding
figure of ray drawing
neuropsychological test
for visuospatial ability
either copy or draw from memory
single dissociation
patient is spared in one task and impaired in another
classical single dissociation
normal range in spared task
strong single dissociation
impaired in both but significantly more impaired in one
double dissociation
2 or more single cases with complementary profiles
classic single dissociation - patient CF
- stroke
- became left handed
- omitted vowels
- another patient made consonant errors
strong single dissociation - semantic dementia and frontotemporal dementia
- SD - more impaired in semantic tasks than others
- frontotemporal - more impaired in social than non-social tasks
why - series of single case studies
cannot average together as same lesions may cause different effects
can group patients for 3 reasons
- syndrome
- behavioural symptom
- lesion location
