Higher Cortical Functions BLOCK 3 –

Higher Cortical Functions BLOCK 3 – 2011-12
Robert R. Terreberry, PhD Room 142 Ph

Association Fibers Corticocortical Connections  cortex parts talking with each other Cortical afferents from other cortical areas fall into two general classes: Association fibers from the same hemisphere (do not cross midline) Commissural fibers from the contralateral hemisphere (cross midline) Superior longitudinal (arcuate) fasciculus  language (sensory and motor skills) Frontal  parietal, temporal, and occipital Superior occipitofrontal fasciculus  Connects the frontal and occipital lobes Parallels the corpus callosum over much of its length and is often called the “subcallosal bundle” Inferior occipitofrontal fasciculus Connects the frontal lobe with the temporal and occipital lobes Fibers that peel off the inferior occipitofrontal fasciculus to enter the temporal lobe are called the uncinate fasciculus Cingulum (cingulum bundle)  Found within the cingulate gyrus An association bundle of the limbic system which connects the septal area and the parahippocampal gyrus Have these association fibers in both hemispheres

Diffusion Tensor Imaging
Association Fibers – Diffusion Tensor Imaging No test Q

Anterior Commissure Anterior Commissure
Small, compact bundle that crosses the midline rostral to the columns of the fornix Connects regions of the middle and inferior temporal gyri, as well as the olfactory tracts and bulbs Anterior Commissure

Corpus Callosum By far the largest fiber bundle in the human brain – more than 300 million fibers Most fibers interconnect homologous regions of the cortex in the two hemispheres

Corpus Callosum B G S R Rostrum
Continuous with the lamina terminalis; forms anterior wall of third ventricle Genu Fibers interconnecting the anterior parts of the frontal lobes Body Fibers interconnecting the remainder of the frontal and parietal lobes Splenium Fibers interconnecting regions of the temporal and occipital lobes Impt for vision (occipital lobe = primary visual cortex)

Posterior Commissure Posterior Commissure
Located at the diencephalic-mesencephalic junction, rostral to the superior colliculus (pineal gland just behind it) Fibers in this commissure connect the pretectal nuclei, not cortical areas Functions in the pupillary light reflex (get direct but not consensual response)

Lateral Fissure Asymmetries
The lateral (Sylvian) fissure extends farther posterior on the left side than on the right and it rises more steeply on the right than the left Language tends to be localized in one hemisphere  wernicke’s and broca’s area in just one hemisphere

Planum Temporale Larger Left hemisphere = 65% Right hemisphere = 11%
Heschl’s = primary auditory complex planum temporale, part of the superior temporal gyrus posterior to the primary auditory cortex, is considerably larger on the left side than the right side in 65% of human brains, and larger in the right side in only 11% of human brains planum temporale is significantly larger in individuals with “perfect pitch” when compared to other individuals

Gender Differences Males Asymmetric poles Females Symmetric poles

Gender Differences Females tend to have larger, more bulbous spleniums of their corpus callosums compared to the spleniums seen in male brains (female left, males R) The larger splenium has more connections  interconnects visual cortices

Cerebral Dominance Dominant Non-dominant Language/Speech Math skills
Problem solving Processing sign language Non-dominant Spatial relationships Music and poetry Artistic ability Emotion

Cerebral Dominance 90-95% right handed people = left hemisphere dominance 65-75% left handed people = left hemisphere dominance True ambidextrous people 60% left dominance 30% right dominance 10% equal dominance Handedness is not a 100% accurate assessment of cerebral dominance Wada testing 1. Important clinical test done prior to neurosurgery, allows for localizing functions within a cerebral hemisphere 2. Temporarily anesthetizes one cerebral hemisphere a. Patient is awake, lying on their back, keeping arms raised in the air b. Sodium amytal (fast-acting barbiturate) is slowly injected into one carotid artery c. Patient counts out loud backwards from 100 by threes 3. Within seconds dramatic effects are seen a. Arm opposite to side of the injection falls limp b. Patient stops counting If the injection is into the non-dominant hemisphere, the patient stops counting for a few seconds, and then resumes counting If the injection is into the dominant hemisphere, the patient stops counting for a few minutes (the duration of the drug’s effect)

Language Areas Central Sulcus Precentral Gyrus Postcentral Gyrus
Arcuate Fasciculus Angular Gyrus Broca’s Area 44 & 45 Wernicke’s Area 22 Broca’s Area 1. Areas 44 & 45 of Brodmann’s scheme 2. Located in the opercular and triangular portions of the inferior frontal gyrus 3. Sometimes called the “motor speech” area 4. Concerned with the motor skills necessary for the generation of propositional language – grammar, syntax, semantics 5. Projects to areas of the primary motor cortex for the execution of the articulation and phonation of speech – the motor processes of speech, as well as the processes for written language 6. Receives inputs from Wernicke’s area via the superior longitudinal (arcuate) fasciculus Wernicke’s Area 1. Area 22 of Brodmann’s scheme 2. Located in superior and middle temporal gyri, posterior to the primary auditory cortex 3. Sometimes called the “sensory speech” area 4. Contains the mechanisms for the understanding, comprehension and formulation of propositional language 5. Receives inputs from auditory, visual and somatosensory cortices Projects via the superior longitudinal (arcuate) fasciculus to Broca’s area Speech doesn’t = language Lateral Fissure Superior Temporal Gyrus

SPEECH EXAMINATION Speech is mechanical aspect of oral communication
VOLUME RATE Normal rate in English is wpm ARTICULATION PROSODY INITIATION 1. Volume a. May be increased (hyperphonia) with auditory problems (deaf) b. May be decreased (hypophonia) with basal ganglia disorders or peripheral nerve problems (parkinsons) 2. Rate Normal rate of verbal output in English is words per minute Rate may increase in Wernicke’s aphasia or decrease in Broca’s aphasia 3. Articulation Defect may result in stereotyped speech errors, such as repeating the same errors when trying to produce certain sounds – seen in dysarthria Paraphasic speech involves substituting letters in a variable pattern Not the same as a dysarthria 4. Prosody a. Should assess the inflection, affective intent and pragmatic intent (humor, sarcasm, etc…) b. Products of the non-dominant hemisphere 5. Initiation The timing of speech initiation is related to the function of the supplementary motor area (SMA)

SPEECH DISORDERS DYSARTHRIA Disturbance in articulation Flaccid
Spastic Ataxic DYSPHONIA Disturbance in phonation Laryngitis Dysarthria 1. Defined as a disturbance in articulation a. Inability to form or produce understandable speech due to lack of motor control over peripheral structures 2. Several different forms have been described including: a. Flaccid Due to LMN disease – either brainstem nuclei or peripheral nerves b. Spastic Due to UMN disease – cortical or corticobulbar lesions c. Ataxic Commonly seen after cerebellar disease 3. Note that patients retain their language ability despite this speech disturbance B. Dysphonia 1. Defined as a disturbance in vocalization or phonation a. Inability to vocalize (loss of voice) due to a disorder of the larynx or its innervation b. Most common cause of decreased voice is laryngitis c. May also be due to damage to the superior laryngeal nerve, pathology of the vocal cords or laryngeal cancer 2. Note that patients retain their language ability despite this speech disturbance

SPEECH DISORDERS PHONIC TICS / VOCALIZATIONS Simple Tics
Inarticulate sounds or noises Complex Tics Articulate words, phrases or sentences Echolalia Coprolalia Simple tics Expressed as inarticulate noises and sounds (throat clearing, grunts, coughs, shouts or snorts) Complex tics Expressed as articulate words, phrases or sentences Often seen in Tourette’s syndrome Several different types have been described Echolalia Involuntary repetition of the last sound, word, phrase or sentence of another person Echoed phrase may be the only verbal output the patient may offer Coprolalia Involuntary utterance of socially unacceptable or obscene words, phrases or sentences

SPEECH DISORDERS STUTTER
Developmental problem, greater incidence in males Repetition of first syllable is machine-gun like Initial sound is followed by silence = Stammer The most common stutter is developmental Characterized by the involuntary repetition of the first syllable of a word May be a machine gun-like repetition – stutter Initial vocalization of the word is followed by a prolonged silence – stammer Both physical and emotional discomfort accompanies these situations Although no definitive anatomical sites have been identified that result in stuttering, it is thought that stuttering is the result of a struggle for cerebral dominance Pts can usually grow out of it, but if a really bad case can take years and lots of therapy to grow out of it

LANGUAGE EXAMINATION Language is cognitive aspect of symbolic communication EXPRESSIVE SPEECH Spontaneous Conversational COMPREHENSION of SPOKEN LANGUAGE Conversation Simple or complex commands Yes or No questions

LANGUAGE EXAMINATION REPETITION NAMING READING WRITING Out loud
For comprehension WRITING Dictation Command Copying 47 min Expressive speech Observe the spontaneous or conversational speech of the patient Comprehension of spoken language a. Can be assessed several ways Engage the patient in ordinary conversation Ask the patient to follow simple or complex commands Ask the patient questions that only require yes or no answers Ask the patient to point to objects Repetition a. Request the patient to repeat numbers, words and sentences Naming a. Test ability to name objects, body parts and geometric figures Reading a. This tests both reading out loud and reading for comprehension 6. Writing a. Examiner assesses writing to dictation and to command (e.g. describe your job) as well as copying b. Writing provides another sample of expressive language and permits evaluation of spelling, syntax, visuospatial layout and writing mechanics

BROCA’S APHASIA NON-FLUENT, MOTOR OR EXPRESSIVE APHASIA
SPONTANEOUS SPEECH Non-fluent, telegraphic, often dysarthric Greatly reduced - 10 wpm COMPREHENSION Intact, mild difficulty with complex grammatical phrases REPETITION Impaired AFTER BREAK The term aphasia has become the general heading for a broad class of language dysfunctions caused by neurological disorders Most aphasias can be classified after evaluating spontaneous speech, repetition and comprehension Verbal output is greatly reduced – often less than 10 words per minute (normal is words per minute) Verbal output is sparse, poorly articulated and produced with considerable effort Hesitant, distorted output Sentences are very short, often only a single word Even so, the output often conveys significant information Verbal output is telegraphic

BROCA’S APHASIA NAMING READING WRITING
Impaired Prompting helps significantly READING Often impaired WRITING Impaired, dysmorphic, dysgrammatic Verbal output is agrammatic Near absence of syntactical words – prepositions, articles and adverbs Words produced are usually nouns, action verbs or descriptive adjectives Naming is poor, but prompting helps significantly Comprehension of spoken language is significantly better than verbal output Some difficulties are often encountered with comprehension of verbal language Broca’s aphasics often have difficulty with the words that they tend to leave out of their own verbal output Writing is abnormal, both to dictation and copying of written material

BROCA’S APHASIA Anterior distribution of left middle cerebral artery
In dominate hemisphere  issues with MCA

BROCA’S APHASIA Can only describe in very few words

WERNICKE’S APHASIA FLUENT, SENSORY OR RECEPTIVE APHASIA
SPONTANEOUS SPEECH Fluent, often increased, paraphasias common, usually not dysarthric Often meaningless - Neologisms COMPREHENSION Impaired REPETITION In parietal lobe area (near auditory cortex) Verbal output is normal or increased Articulation is normal Production requires little or no effort Prosody tends to be preserved Sentences tend to be devoid of meaningful words Almost no meaningful information is conveyed Speech is sometimes called “empty speech” Paraphasia is common Substitution of syllables or entire words for others Words may be substituted by meaningless, nonsense words – neologisms “Jargon aphasia” is severe form with rapid, incomprehensible verbalization Comprehension of spoken language is disturbed Severity of this deficit is variable Patients can sometimes understand a few words and even short sentences

WERNICKE’S APHASIA NAMING READING WRITING Impaired
Impaired for both comprehension and reading out loud WRITING Well-formed letters in meaningless combinations Reading out loud and reading comprehension are abnormal Writing consists of well-formed letters in meaningless combinations Wernicke’s aphasics have an increased verbal output and tend to speak incessantly Often a person with this deficit will not realize their speech is defective or meaningless and continue to talk as if nothing is wrong

WERNICKE’S APHASIA Posterior distribution of left middle cerebral artery Issues in dominant hemisphere  PCA

WERNICKE’S APHASIA

CONDUCTION APHASIA SPONTANEOUS SPEECH COMPREHENSION REPETITION
Fluent, some hesitancy May be paraphasic - meaningless COMPREHENSION Intact REPETITION Severely impaired Lesion involves arcuate fasciculus in dominant hemisphere Inferior parietolobule region Lesion involves the connections (arcuate fasciculus) that run between Wernicke’s and Broca’s areas in the dominant hemisphere Both areas are intact, but the flow of information between them is interrupted Characterized by: a. Difficulty repeating Verbal output is fluent and paraphasic (but less than seen in Wernicke’s aphasia) b. Articulation is excellent c. Comprehension of spoken language is intact d. Reading out loud is poor, but reading silently for comprehension is intact e. Writing is disturbed to some extent Most often words and letters are substituted, misspelled or misplaced f. Spontaneous speech may be meaningless fluent jargon (like Wernicke’s aphasia), but unlike with Wernicke’s aphasia, comprehension of the spoken and written word is good and intact

CONDUCTION APHASIA NAMING May be moderately impaired READING
Reading out loud severely impaired Reading comprehension usually good WRITING Variable deficits

TRANSCORTICAL MOTOR APHASIA
SPONTANEOUS SPEECH Non-fluent, resembles Broca’s aphasia COMPREHENSION Intact REPETITION Intact – better than Broca’s aphasics NAMING Limited ability READING Often impaired WRITING Impaired Lesion involves anterior watershed zone in dominant hemisphere, or ACA infarct superior to Broca’s area – usually white matter 1. Lesion involves anterior watershed zone of dominant hemisphere or ACA infarcts anterior and superior to Broca’s area Lesion often encompasses cortical white matter deep to SMA, above and lateral to the frontal horn of the lateral ventricle 2. Resembles Broca’s aphasia, but repetition is good to excellent Impaired verbal fluency (non-fluent) with normal comprehension, but repetition is spared (often better than in patients with Broca’s aphasia) Usually develops after a period (days to weeks long) of muteness – may be seen in patients recovering from Broca’s aphasia Patient has limited, agrammatical and considerably efforted spontaneous speech Limited ability to name objects and to compose word lists Major deficits seen in answering open-ended questions and in narrative storytelling and writing Ability to repeat spoken and written sentences is retained Articulation is usually normal as is comprehension

TRANSCORTICAL SENSORY APHASIA
SPONTANEOUS SPEECH Fluent, resembles Wernicke’s aphasia COMPREHENSION Impaired REPETITION Intact, often exhibit pure echolalia NAMING READING WRITING Lesion involves posterior watershed zone in dominant hemisphere – posterior and superior to Wernicke’s area 1. Lesion involves posterior watershed zone of dominant hemisphere a. Lesion often encompasses parietal and temporal areas, posterior and superior to Wernicke’s area 2. Clinically similar to Wernicke’s aphasia, but intact repetition a. Normal verbal fluency, impaired comprehension b. Fluent verbal output with considerable paraphasia including both neologisms and semantic substitutions c. Patient often exhibits echolalia d. Naming is disturbed e. Reading out loud may be preserved but is usually contaminated with paraphasic errors f. Comprehension and writing are abnormal

TRANSCORTICAL MIXED APHASIA
SPONTANEOUS SPEECH Non-fluent, resembles global aphasia COMPREHENSION Impaired REPETITION Intact, often limited to 3-4 words, well below normal NAMING READING WRITING Lesion involves both anterior and posterior watershed zones in dominant hemisphere 1. Lesion involves both anterior and posterior watershed zones in dominant hemisphere 2. equivalent to global aphasia, but repetition is preserved a. Patients don’t speak unless spoken to b. Exhibit true echolalia c. Repetition, although well-preserved when compared to other aphasias, is limited and well below normal Number of words in a sentence that can be repeated is often limited to three or four

APHASIA SQUARE Good Comprehension Poor Comprehension Fluent Speech
Wernicke’s Aphasia Fluent Speech Conduction Aphasia Transcortical Sensory Aphasia Broca’s Aphasia Mixed Transcortical Aphasia Non-Fluent Speech Transcortical Motor Aphasia POOR REPETITION GOOD

ANOMIC APHASIA (Anomia)
SPONTANEOUS SPEECH Fluent, some pauses, circumlocution COMPREHENSION Intact REPETITION NAMING Impaired, but prompting helps READING WRITING Intact, except for anomia Anomic aphasia  can’t name things, can describe it but can’t come up with what it actually is (Ex. Pen) (circumlocution  can tell everything about it but not what it is….go in circles to avoid direct answer) 1. Also known as amnestic aphasia or nominal aphasia a. Output tends to be vague with a lack of substantive words Also termed “empty speech” 2. Principal deficit is in naming a. Excessive word-finding pauses – hestitations b. A purely anomic patient will have normal comprehension and be able to speak almost normally in spontaneous casual conversation c. When confronted with objects or when trying to think of a word or name, the patient will falter badly 3. Comprehension is relatively well-preserved 4.Involves lesions of the angular gyrus in the dominant hemisphere

GLOBAL APHASIA SPONTANEOUS SPEECH COMPREHENSION REPETITION NAMING
Non-fluent COMPREHENSION Impaired REPETITION NAMING READING WRITING Global aphasia 1. All language functions are seriously impaired a. Verbal output is very limited (but the patient is not mute) b. Comprehension is often better than verbal output, but it is also seriously disturbed 2. Communication may be attempted with a symbol system 3. Results from widespread damage to the dominant hemisphere involving most of the language areas

Other Higher Function Problems
Alexia Agraphia Prosopagnosia Aprosodia Motor Sensory Agnosia Apraxia Alexia Loss of the ability to read May be coupled with inability to write (agraphia) Visual information has lost access to Wernicke’s area Lesion usually involves connections in and around the angular gyrus in the dominant hemisphere Dyslexia is an incomplete alexia and is characterized by an inability to read more than a few lines with understanding Agraphia Defined as a loss or impairment of the ability to produce written language due to brain dysfunction Several different types have been described Lesion usually involves the inferior parietal lobule, especially the angular gyrus in the dominant hemisphere Micrographia is often seen in Parkinson's disease and is not the same as agraphia Prosopagnosia Inability to recognize familiar faces Patient may not be able to recognize a previously known person’s face and in some cases has difficulty recognizing their own face in a mirror Patients may have trouble recognizing that the face is in fact a face; they may see it as another object for example Due to bilateral lesions of the temporal lobes Aprosodia Prosody is the rhythmic and more-or-less musical aspects of speech, may be non-verbal The non-dominant (minor) hemisphere is thought to play a role in generating and comprehending prosody Area of the frontal lobe generates prosody Posterior temporoparietal region comprehends prosody Motor aprosodia is the inability to convey emotions by voice or gestures (even though the emotions exist) – monotone speech Sensory aprosodia involves difficulty comprehending the emotional content of speech or the gestures of others Agnosia The inability to recognize or be aware of an object when using a given sense – even though that sense is functionally intact Several different types have been described according to the sensory modality that is affected Sensory or tactile agnosia Referred to as astereognosis Characterized by: Lesions in the superior parietal lobule, may occur in either hemisphere, with contralateral loss of sensory discrimination – i.e. left hemisphere lesion, difficulty identifying objects with right hand Inability to recognize objects by touch alone (secondary somatosensory processing affected) Appropriate tactile pathways are intact (primary somatosensory processing intact) Identification of the object may be accomplished with other senses (vision, hearing) Visual agnosia Lesions of the visual association cortices (Areas 18, 19) in the dominant hemisphere Inability to recognize objects by sight alone Patient may still be able to recognize object tactily Apraxia The inability to correctly perform certain learned, skilled movements on command, in the absence of elementary sensory – motor deficits Motor and sensory pathways are intact Patient usually able to perform the same action in a different context (reflex) Several different types have been described; we will discuss 3 of the more common types Kinetic (Limb-kinetic) apraxia Involves a lesion of the premotor cortex Characterized by difficulties in fine motor control Loss of ability to make finely graded, precise individual finger movements Finger tapping test Picking up a straight pin from a desktop Ideomotor apraxia Involves a lesion of the supramarginal gyrus in the dominant (major) hemisphere Characterized by the inability to perform many complex tasks on command Spatial and temporal errors Orientation of body or tool is often incorrect Most errors occur when patient is asked to pantomime an action Given actual objects and appropriate context, patients usually perform much better Ideational apraxia Seen in degenerative dementia (frontal lobe dysfunction) Characterized by the inability to perform a series of acts to obtain a goal (making a sandwich)

Prefrontal Cortex A. Anterior portion of the frontal lobe, this area does not elicit somatic motor movements when stimulated B. This part of the brain has expanded dramatically during mammalian evolution C. Important in determining affective reactions to present situations based upon past experiences (right from wrong) D. Monitors behavior and exercises control based on higher mental faculties such as judgment and foresight E. Lesions of prefrontal cortex result in: Inappropriate social behavior Difficulties in adaptation and loss of initiative  cannot make a decision “Phineas Gage syndrome”

Phineas Gage

Hemineglect - Normal Neglect Syndromes
Lesions of the non-dominant parietal lobe (superior parietal lobule) often lead to a lack of appreciation of the spatial aspects of all sensory input from the contralateral side of the body and the contralateral visual field Although sensations are relatively intact, patients sometimes ignore half of their body – contralateral neglect – hemineglect More severe following lesions in the non-dominant hemisphere than that seen after lesions in the dominant hemisphere; reason for this is largely unknown Lack of awareness of the contralateral half of personal space or the contralateral side of their body Failure to dress (dressing apraxia), groom, etc... the contralateral side of their body Often associated with anosognosia – denial of the deficit, patients often deny that the illness exists as well as the contralateral side of their body

Hemineglect - Lesion

Hemineglect

Split Brain – Chimeric Testing
Involves severing the corpus callosum either surgically or due to a lesion Experimental commissurotomies have contributed to our knowledge of localization of cortical functions and the role of the corpus callosum in the interhemispheric transfer of information Patients who have undergone this procedure exhibit no outward neurological deficits – they look and act “normal” Deficits of this lesion – disconnection syndromes Inability of a blindfolded patient to match an object held in one hand with that held in the other hand Inability, when blindfolded, to correctly name objects placed in the left hand (anomia) because information cannot reach Wernicke’s area in the left hemisphere (Assume this patient is left-hemisphere dominant) Note: If one reverses the test, i.e. object in the right hand, blindfolded, naming the object is relatively easy because information has access to Wernicke’s area on the same side.

ALEXIA without AGRAPHIA
SPONTANEOUS SPEECH Intact COMPREHENSION REPETITION NAMING Impaired, especially colors READING Impaired, some sparing of letters WRITING Alexia without agraphia Due to a lesion of the posterior cerebral artery and destruction of the dominant visual cortex and the splenium of the corpus callosum Language areas are cut off from visual inputs, thus the patient is able to write (no agraphia) but not read (alexia) anything – even the words they have just written!

ALEXIA without AGRAPHIA

I need a volunteer to read a short passage to the class.

Spelling and Reading Comprehension
Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a word are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can still raed it wouthit a porbelm. Tihs is bcuseae the hmuan mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe.

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