Podcast
Questions and Answers
What type of visual neglect is most commonly associated with lesions in the nondominant parietal lobe?
What type of visual neglect is most commonly associated with lesions in the nondominant parietal lobe?
During the clock drawing test, what indicates the presence of neglect?
During the clock drawing test, what indicates the presence of neglect?
What deficit might a patient exhibit if they have frontal lobe dysfunction while asked to draw alternating shapes?
What deficit might a patient exhibit if they have frontal lobe dysfunction while asked to draw alternating shapes?
What task tests the patient's ability to suppress inappropriate behaviors?
What task tests the patient's ability to suppress inappropriate behaviors?
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Which reflex may re-emerge in patients with frontal lobe disease?
Which reflex may re-emerge in patients with frontal lobe disease?
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What does impersistence in a patient indicate?
What does impersistence in a patient indicate?
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What might indicate a patient's difficulty with task switching?
What might indicate a patient's difficulty with task switching?
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Which area is least likely to produce neglect when lesions occur on the left side?
Which area is least likely to produce neglect when lesions occur on the left side?
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What is the primary target of the axons in the fornix?
What is the primary target of the axons in the fornix?
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Which structure is thought to be the brain's pleasure center?
Which structure is thought to be the brain's pleasure center?
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How does the hippocampal formation influence memory despite its focused subcortical projection?
How does the hippocampal formation influence memory despite its focused subcortical projection?
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What is the role of the mammillary bodies in the brain's circuitry?
What is the role of the mammillary bodies in the brain's circuitry?
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What condition is characterized by significant degeneration of the mammillary bodies?
What condition is characterized by significant degeneration of the mammillary bodies?
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How many myelinated axons does the fornix contain on each side?
How many myelinated axons does the fornix contain on each side?
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The cingulate gyrus receives projections directly from which structure?
The cingulate gyrus receives projections directly from which structure?
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What type of connections does the entorhinal cortex provide to other brain areas?
What type of connections does the entorhinal cortex provide to other brain areas?
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What does the glabellar reflex indicate when it does not result in habituation in a patient?
What does the glabellar reflex indicate when it does not result in habituation in a patient?
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Which symptom may indicate a frontal lobe lesion?
Which symptom may indicate a frontal lobe lesion?
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How can logic and abstraction be evaluated in a patient?
How can logic and abstraction be evaluated in a patient?
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Which of the following is a method to screen for delusions?
Which of the following is a method to screen for delusions?
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What condition can cause thought deficits besides primary psychiatric disorders?
What condition can cause thought deficits besides primary psychiatric disorders?
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Which clinical tool consideration is crucial for assessing mental status?
Which clinical tool consideration is crucial for assessing mental status?
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What symptoms may arise from psychiatric disorders in relation to neurologic symptoms?
What symptoms may arise from psychiatric disorders in relation to neurologic symptoms?
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Which of the following best describes the nature of logic and abstraction functions?
Which of the following best describes the nature of logic and abstraction functions?
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What syndrome is characterized by features including hyperorality and hypersexuality due to bilateral lesions in the amygdala?
What syndrome is characterized by features including hyperorality and hypersexuality due to bilateral lesions in the amygdala?
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What is a common result of bilateral lesions in the primary visual cortex?
What is a common result of bilateral lesions in the primary visual cortex?
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Which visual processing deficit is associated with an inability to recognize faces?
Which visual processing deficit is associated with an inability to recognize faces?
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What describes the inability to perceive colors, typically resulting in a view of the world in shades of gray?
What describes the inability to perceive colors, typically resulting in a view of the world in shades of gray?
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What condition is characterized by patients being unaware of their visual deficits due to bilateral lesions of the primary visual cortex?
What condition is characterized by patients being unaware of their visual deficits due to bilateral lesions of the primary visual cortex?
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Lesions in which area are associated with color agnosia?
Lesions in which area are associated with color agnosia?
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Which condition may occur alongside achromatopsia and involves recognition of facial components but not the entire face?
Which condition may occur alongside achromatopsia and involves recognition of facial components but not the entire face?
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What term describes a visual processing deficit where recognition of faces is inhibited, but recognizing individuals by other traits is possible?
What term describes a visual processing deficit where recognition of faces is inhibited, but recognizing individuals by other traits is possible?
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Which brain structure is primarily involved in planning and sequencing?
Which brain structure is primarily involved in planning and sequencing?
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What is the main function of the orbitofrontal cortex?
What is the main function of the orbitofrontal cortex?
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Given the symptoms of social withdrawal and apathy in a 62-year-old patient, which disorder should be a primary concern?
Given the symptoms of social withdrawal and apathy in a 62-year-old patient, which disorder should be a primary concern?
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Which brain region is primarily associated with conflict monitoring?
Which brain region is primarily associated with conflict monitoring?
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Which cognitive function is not primarily attributed to the orbitofrontal cortex?
Which cognitive function is not primarily attributed to the orbitofrontal cortex?
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In the context of behavioral changes, what kind of impulsivity is often seen in patients with frontotemporal dementia?
In the context of behavioral changes, what kind of impulsivity is often seen in patients with frontotemporal dementia?
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Which symptom is least associated with the orbitofrontal cortex's role in emotional processing?
Which symptom is least associated with the orbitofrontal cortex's role in emotional processing?
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Which of the following is not a typical outcome of anterior cingulate dysfunction?
Which of the following is not a typical outcome of anterior cingulate dysfunction?
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Study Notes
The Fornix
- The axons in the fornix terminate mainly in the mammillary bodies and septal nuclei.
- The septal nuclei are thought to be the brain’s pleasure center and play an important role in motivated behaviors and reinforcing positive social interactions.
- The septal nuclei project back to the hippocampal formation and may help regulate memory formation during certain behavioral states.
- The mammillary bodies project to the anterior thalamic nucleus through the mammillothalamic tract.
- The anterior thalamic nucleus projects to the cingulate gyrus, which projects back to entorhinal cortex.
- Given the fornix’s size and the diverse connections of the hippocampal formation, the hippocampus can influence virtually all association areas of the temporal, parietal, and frontal lobes, as well as some higher-order sensory areas.
Korsakoff Syndrome
- In Korsakoff syndrome, there is significant degeneration of the mammillary bodies and the medial thalamus.
- Construction tasks that involve drawing complex figures or manipulating blocks or other objects in space may be abnormal.
- The clock drawing test can be a useful tool to assess for neglect and construction tasks as visual neglect can result in drawing numbers on one side of the clock face only or not bisecting a line drawn across the clock in the center.
Frontal Release Signs
- Frontal lobe dysfunction can interfere with task switching, resulting in perseveration, e.g. drawing the same shape repeatedly when asked to alternate shapes.
- Difficulty switching between movements on the manual sequencing task, in which the patient is asked to repeat a sequence of hand movements, may also occur.
- Impersistence, or inability to sustain an action, e.g. holding their arms up, is a related deficit.
- The Auditory Go-No-Go Test can be used to test their ability to suppress inappropriate behaviors and involves tapping a finger in response to one tap, but staying still in response to two taps.
- Frontal release signs are abnormal reflexes that re-emerge in the setting of frontal lobe disease and are related to primitive reflexes seen in normal infants.
- The grasp reflex involves assessing for a grasp response when fingers or a hand are placed into the patient’s hand.
- The snout reflex is elicited by tapping on the patient’s upper lip, causing contraction of the muscles around the mouth.
- The palmomental reflex is induced by tracing along the thenar eminence up to the base of the thumb causing ipsilateral contraction of the orbicularis oris and mentalis muscles.
- The glabellar reflex, where repeated tapping on the forehead does not result in habituation and suppression of eye blink, may be abnormal in Parkinson disease.
- Frontal lobe lesions may also lead to abulia or changes in personality or judgment.
Logic and Abstraction
- Logic and abstraction can be assessed by asking a patient to solve simple word problems, recognize patterns, and interpret proverbs.
Thought
- Ask the patient about auditory or visual hallucinations and if they have any special abilities or powers to screen for delusions.
- Insight is assessed by testing the patient’s ability to appropriately recognize a nonsense question, such as “Do helicopters eat their young?”
Mood
- Screen for signs of depression, anxiety, or mania.
- Psychiatric disorders may provoke neurologic symptoms in the setting of somatization or conversion disorders, where patients may present with pain, numbness, weakness, or seizure-like activity not due to a neurologic deficit.
- Neurologic disorders may produce confusional states and bizarre behaviors.
Clinical Tools
- Multiple clinical tools exist to help clinicians to assess mental status and trend cognitive function over time.
- Selection of the tool should consider its generalizability and applicability irrespective of language, education, or cultural background, as well as standard measures of inter-rater reliability, test-test reliability, sensitivity, and specificity.
- The time needed to complete the assessment and cost of use may also affect which tool is used.
Klüver-Bucy Syndrome
- Bilateral lesions in the amygdala can produce Klüver-Bucy syndrome.
- Klüver-Bucy syndrome is a neuropsychiatric syndrome characterized by generally placid behavior accompanied by hyperorality, hypersexuality, binge eating followed by purging behavior, and visual agnosia to faces and objects.
- Seizures that involve the amygdala can cause an emotional aura of fear and panic.
Visual Association Cortex
- Lesions in the visual association cortex can result in multiple deficits in visual processing.
- Anton’s syndrome is caused by bilateral lesions of the primary visual cortex that result in cortical blindness and complete visual loss on confrontation testing but patients demonstrate anosognosia of their deficits.
- Visual loss anosognosia may also occur with combined occipital and frontal lesions or occipital and nondominant parietal lesions.
- Prosopagnosia is an inability to recognize people by their faces, typically due to a lesion in the bilateral fusiform gyri in the inferior occipitotemporal cortex.
- Patients with prosopagnosia can identify the components of faces and can recognize individuals by clothing, gait, or voice, but are unable to recognize the components of the face as a whole.
- Prosopagnosia is often associated with achromatopsia and occasionally alexia.
- Achromatopsia is a deficit in the ability to perceive color in part or all of the visual field, presenting in an inability to name, identify, or match colors presented visually.
- Patients are typically aware of the deficit and describe the affected vision as appearing in shades of gray.
- When the entire visual field is involved, achromatopsia is caused by lesions in bilateral inferior occipitotemporal cortex and is typically accompanied by prosopagnosia.
- Hemiachromatopsia is caused by lesions in the contralateral inferior occipitotemporal cortex.
- Color agnosia (aka color anomia) is caused by lesions of the primary visual cortex of the dominant hemisphere extending into the corpus callosum and is associated with alexia without agraphia and right hemianopia.
Self-Assessment Question Answers
- Question 1: Planning and sequencing are mediated by the dorsolateral prefrontal cortex (A).
- Question 2: The orbitofrontal cortex is responsible for monitoring of emotional response to external stimuli (B).
- Question 3: The patient's symptoms, including social withdrawal, apathy, changes in personality, and impulsive behavior, are consistent with behavioral variant of frontotemporal dementia (D). While other conditions may present with some overlapping symptoms, these are not typical presentations.
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Description
This quiz explores the structure and function of the fornix, including its connections to the mammillary bodies and septal nuclei. Additionally, it covers Korsakoff syndrome and its impact on brain structures. Test your knowledge on these important neuroanatomical concepts.
