π― Objectives
The students would be familiarized with the role of higher order brain functioning π§ β‘. These are disorders of speech π«π£οΈ, motor π«π€, and sensory π«ποΈπ functions i.e., apraxia's and disorders related to memory π and amnesias π«π.
π Brain Correlates
- Language π£οΈ Speech Production π¬ Comprehensions π, Aphasias π«π£οΈ
- Visuospatial ποΈπ, the man who mistook his wife for a hat? π©β
- Apraxia's π«π€ (Neuropsychological tools π§)
- Brain correlates of Learning and Memory π§ πΎ, Amnesia π«π, Verbal/Nonverbal memory π
- (Neuropsychological tools π§π§ͺ)
π Aphasia and Dyslexia
These are related π since spoken words transferred to written language π. Reading π and writing βοΈ are closely tied to listening π and speaking π£οΈ, but reading and writing use the auditory modality π.
Wernicke's aphasia is accompanied by dyslexia πβ (difficulty reading/writing π«βοΈ).
π Language-Specific Dyslexia Effects
Interestingly, there are more dyslexics with Wernicke's aphasia in English and western language π¬π§ not in Chinese π¨π³ where each word is represented individually γοΈ or in sign language π which is a spatial modality not auditory π.
Chinese aphasics π¨π³ retain the ability to write accurately βοΈβ . Japanese language π―π΅ has two forms:
- Kanji: symbols, pictographs π―, adopted from Chinese, visual representation of concepts ποΈ such as house would be in the shape of Pagoda π―
- Kana: symbols are acoustic, Phonetic representations π they are the sound π΅
π―π΅ Japanese Language Studies
Kana is the sound π and therefore auditory mode π, Kanji is visual mode ποΈ.
Sasanuma 1975 π¨βπ¬ reported that left temporal lobe lesions affected writing Kana symbols π«βοΈ but not Kanji as visual cortex is involved ποΈ.
| Japanese Language π―π΅ | Mode πποΈ | Brain Area π§ |
|---|---|---|
| 3 phonetics: Kana π | Auditory π | Left temporal lobe π§ |
| 1 pictograph: Kanji π― | Visual ποΈ | Visual cortex π§ |
π§ Sound-Based Language
Generally, most languages use sound, acoustic signals and cues π when we write or look and recite ππ£οΈ. We remember nursery rhymes π΅ to remember the correct spellings of words π.
The question then is π€ if we are so dependent on sound for language what about the deaf π§? Interestingly, the deaf are not dyslexics or receptive aphasic β, they can read without phonetics πβ . Braille π€² is a language of the blind π¦― (touch language π€).
π«π£οΈ Aphasias Related to Speech
There are a wide range of disorders π and even within the two major aphasias π£οΈ the characteristics differ depending on where the areas are damaged β οΈ. We will discuss some of the aphasia briefly π:
π Conduction Aphasia
Conduction Aphasia: This is produced by damage to the inferior parietal zone which disconnects the axonal fibers connecting Broca's and Wernicke's areas π«π. These patients have meaningful paraphrastic speech π£οΈ, somewhat fair comprehension π but poor repetition πβ. They can repeat single and meaningful words β but not non-meaningful words β.
π·οΈ Anomic Aphasia
Anomic Aphasia: This is the aphasia for specific names π·οΈβ. The difficulty in finding the right word to use, so they use circumlocution π which is going roundabout way π.
π The Stapler Example
A patient with anomia after stroke π₯:
Asked to identify a stapler in the picture: πβ
What is it? π€
"It is used in an office" π’
Yes, but what is it? π€
"It is used to pin papers together" π
Yes, but what is it? π€
"β¦showed how it workedβ¦" π€
Yes, but what is its name? π·οΈβ
Could not give the name π«
β¦After several attemptsβ¦
This illustrates that he knew what it was and what it was used for β but could not name it π·οΈβ.
There are other cortical aphasias β οΈ, Trans cortical aphasia β οΈ, and sub cortical aphasias β οΈ which we will not discuss. I think the whole classification should be enough to give you an idea π.
π Dyslexia: Reading, Writing, Mathematics
The reading and writing disorders are related to the kind of aphasia the patients have π. A patient with Wernicke's aphasia has difficulty in reading πβ and writing βοΈβ and does not comprehend speech πβ. Broca's aphasics have difficulty in reading out aloud π£οΈβ, their writing and speech both are agrammatical πβ.
π Types of Dyslexia
π Alexia with Agraphia
Alexia with Agraphia: This is a difficulty that a person has with both reading πβ and writing βοΈβ. This is caused by damage to the left angular gyrus of the parietal lobe π§ β οΈ. Angular gyrus is at a borderline of the visual, auditory and somatosensory cortices ποΈππ€ and may affect skills involving all three modalities π.
ποΈ Pure Alexia
Pure Alexia: Actually a word blindness π«ποΈπ, alexia without agraphia. The patient can write βοΈβ but cannot read πβ. He writes βοΈ, although he cannot read or recognize the words spelled out π«.
Pure Alexia is a perceptual disorder ποΈβ οΈ similar to pure word deafness πβ, only it is visual ποΈ not auditory π.
π« Agnosia
Agnosia: A disorder related to sensory modalities ποΈπ either auditory π or visual ποΈ.
π Disorders of Auditory Perception: Agnosia
Auditory Agnosia is an impaired capacity to recognize auditory stimuli πβ and perhaps this is a disturbance in perceptual processes π§ β οΈ more than sensations. It appears that there is no problem with the input of information π‘β but giving it meaning or recognizing it πβ. We will discuss only two here π:
π΅ Amusia
Amusia: This has subdivisions in this disorder π΅:
- Tone deafness: The inability to discriminate various tones in musical scales πΌβ
- Music deafness: An impaired recall and recognition of melody or tune πΆβ as well as rhythm and measure and tempo (beat) π₯β
- Receptive amusia: A difficulty in discriminating basic notes of music π΅β and series of notes (pitch) π and rhythm π₯
π Agnosia for Sounds
Agnosia for sounds: This is the inability to identify what different nonverbal sounds mean πβ (classification and difficulty).
For example, different kinds of bells ringing π: church bell βͺ, school bell π«, telephone π - the patient cannot tell the difference β. The sounds may sound all alike or confused with each other π. Basically this is a discrimination and categorization deficit πβ.
These disorders appears to involve bilateral temporal regions π§ .
ποΈ Visual Deficits
These are deficits related to the integration and processing of visual information ποΈπ§ . Agnosia is a failure in recognition π« not due to sensory input (that's all right β ) or intellectual problems (the patient has no intellectual impairment π§ β ).
ποΈ Visual Agnosia
Visual Agnosia: Agnosia for a visual stimulus ποΈ not a seeing deficit (patient can see πβ but cannot put the pieces of the visual input together into a coherent form π§©β). A Very interesting deficit is Prosopagnosia π«π.
π Prosopagnosia
Prosopagnosia (Visual Agnosia for Faces π«π):
First and key thing we have are other people π₯. Whether they are a friend or foe ππ‘. There is a dictionary π of features of faces in which every face is immediately matched π.
Prosopagnosics have difficulty in recognizing a face πβ. They know it's a face but who? π€ These patients report that they are seeing the parts π§©: nose π, eyes ποΈ, lips π but cannot put it together into a coherent whole β.
They recognize that it is a face but have to match and put together the entire feature into a coherent face π.
π§ Neural Basis
In extreme form of this deficit π΅ the patients cannot even recognize themselves in the mirror πͺβ.
This is due to damage to the Inferotemporal region π§ β οΈ. Some patients have difficulty recognizing only familiar faces π¨βπ©βπ§βπ¦β, while others have difficulty with unfamiliar faces π«π€.
They can sometimes use a cue such as a mole or scar to recognize the face π. This is a visual-limbic disconnection πβ especially with familiar faces. This is a Right hemisphere region π§ .
π«π€ Apraxia
Apraxia: These are movement and motor difficulties π«π€ when they are required to perform some action on verbal command π£οΈ. Though these tasks can be performed spontaneously π, they can also be copied without any problems β .
This is bilateral βοΈ, but is usually produced by a left hemisphere lesion π§ β οΈ.
This deficit was first described by Hughlings-Jackson π¨ββοΈ. Apraxia is a Greek Word π¬π·: Praxis which means No Action π«π€.
It is the missing or inappropriate action π«. This is not due to paralysis πͺβ , difficulties in motor movement π¦΅β , understanding instructions β , or motivation πͺβ , but difficulty in carrying out the action which is required β οΈ.
ποΈ Construction Apraxia
Construction Apraxia: This is tested by asking the patient to copy βοΈ, draw π¨, or build with blocks 𧱠a given design π. Both left and right hemisphere damage can result in this β οΈ:
- LH (Left Hemisphere) damage: leads to oversimplification π - very little details β οΈ
- RH (Right Hemisphere) damage: leads to loss of the overall gestalt πβ (the whole picture πΌοΈ)
π¬ Conclusion
We have seen that these deficits are caused by damage to different cortical areas π§ β οΈ. This requires a complex neuropsychological examination π and rehabilitation strategies are developed keeping each patient's individual deficits in mind π―.
π 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