human lesion studies and brain stimulation methods

cognitive neuroscience

what is: edwin smith surgical papyrus?

the oldest known document on spinal injuries

what happened to Phineas Gage?

a metal rod pierced his left eye because of an explosion

how was Phineas Gage after the incident?

he was physically fine

however his personality changed (more impulsive, impatient, capricious (unpredictable), difficulties with planning and following through)- related to executive functions

patient “Tan”?

he was Broca’s patient (so injury to broca’s area)

lost his ability to speak and could only say the syllable "tan" (related to speech- broca’s aphasia)

broca’s aphasia?

it’s an expressive language disorder that affects how you speak (your fluency) but not your understanding of words (your comprehension)

-you know what to say but have trouble speaking

-example: “Me go store buy milk” instead of “I’m going to the store to buy milk.”

where in the brain is broca’s area?

frontal lobe of the dominant hemisphere, usually the left

who developed lobotomy?

-developed by Egas Moniz

-surgical procedure aimed at treating severe mental disorders.

mechanism of lobotomy?

inserting a tool through orbital socket and damaging some of the frontal lobe (shifting the tool left and right)

the thought behind lobotomy?

targeted brain lesions could alleviate certain symptoms of mental disorders

-(lobotomy made patients docile)

who was patient h.m. studied by?

brenda milner

patient h.m?

he had an accident leading to epileptic seizures

they removed his hippocampus to control the seizures, which resulted in anterograde amnesia (was unable to form new memories)

what is corpus callosotomy?

surgical procedure that involves removing/sectioning the corpus callosum, the structure connecting the two hemispheres of the brain

what does corpus callosotomy prevent?

communication between the 2 hemispheres (meaning information to pass)

and epileptic seizures (alleviates them)

what did michael gazzaniga illustrate?

hemispheric specialization

what is hemispheric specialization?

refers to the differential role of the left or right brain side in processing a specific neuronal task/behavior

(this concept highlights how each hemisphere is specialized for certain functions, with the left often associated with language and analytical skills, while the right is linked to spatial abilities and creativity)

how can lesions be?

permanent or reversible

what is the WADA test?

in order to localize memory and language in the brain, they injected sodium amobarbital (anaesthetic) into the left or right arteries of brain hemispheres

wada test: what happened when they injected anaesthetic in the right hand?

the left hemiphere was affected:
-unable to continue counting (language)

wada test: what happened when they injected anaesthetic in the left hand?

right hemisphere affected:

-memory impaired (stm)

what are the conclusions of wada test?

left hemisphere : language

right hemisphere: memory (stm)

what are the 2 treatments for parkinsons disease and essential tremor?

deep brain stimulation(DBS) and MR-guided focused ultrasound (MRgFUS)

what is deep brain stimulation(DBS)?

implating electrodes into specific areas of the brain (nucleus)

the thin wires (electrodes) deliver small electrical pulses to the brain to help regulate abnormal brain activity (works like a pacemaker for the brain)

looking and listening to neuron spiking

what is MR guided focused ultrasound (MRgFUS)?

focused ultrasound waves to heat and destroy tiny areas of brain tissue that are causing problems (guided by MRI scans for precision)

able to identify how effective the stimulation is by monitoring temperature changes (higher spatial resolution)

the main difference between DBS(deep brain stimulation) and MR guided focused ultrasound?

DBS is invasive while the other is non- invasive

what are single case studies?

the data from different patients are not combined; helpful for establishing how cognitive processes might be subdivided

(each patient is described in detail)

what are group studies?

the performance of different patients is combined to yield a group average

helpful for establishing lesion-deficit associations

what is classical dissociation?

perfomance on one task lies within the control range

(patient impaired on task A but not B)

what is strong dissociation?

both tasks fall outside the control range, but one task is significantly more impaired than the other

(patient impaired on both tasks, one being more impaired than the other)

what is the first inference in single dissociation?

task A and B utilize different cognitive processes (with different neural resources)

what is the second inference in single dissociation?

“task demand artifiact”
the patient simply performs one of the tasks suboptimally (basically for other reasons than due to his lesion: eg. patient misunderstood the instructions)

what is the third inference in single dissociation?

task-resource artifact

the 2 tasks share the same cognitive resources, but one task uses it more (relies more heavily/its more difficult)

what is task demand artifact?

the patient simply performs one of the tasks suboptimally (basically for other reasons than due to his lesion: eg. patient misunderstood the instructions)

what is task resource artifact?

the 2 tasks share the same cognitive resources, but one task uses it more (relies more heavily/its more difficult)

what is double dissociation?

two single dissociations that have a complementary profile of abilities

(two patients each showing the opposite impairment)

example of double dissociation?

a patient can write vowels, but struggles with consonants

another can write consonants well, but struggles with vowels

what evidence does double dissociation provide?

that 2 cognitive functions/abilities rely on separate brain systems or processes (each function can be impaired independently of the other)

single dissociation vs strong dissociation

A single dissociation means that damage to a specific brain area impairs one cognitive function but not another, suggesting the functions are separate.

A strong dissociation is a more complex scenario where damage impairs both functions, but one more significantly than the other, further strengthening the idea of separate cognitive processes

what is TMS?

transcranial magnetic stimulation

on what works is TMS based?

faraday’s law of induction

what is faradays law of induction?

a quantitative relationship expressing that a changing magnetic field induces a voltage in a circuit (creates an electric current)

what can and cannot tms target?

tsm can only target cortical areas , doesn’t allow to go into subcortical structures

basically what does tms do?

uses a magnetic field to change the activity of neurons in the brain