Integrating Test Data with other Clinical Information Three Important Principles Avoid the Fallacy of Affirming the Consequent because B often follows A, occurrence of B proves that A has occurred Be Open Minded generate as many reasonable explanations for what you see Apply Occam’s Razor “the most likely explanation for a pattern is the one that requires the least number of unlikely events to account for it “

Errors in Formulation Affirming the Consequent Complains of memory change after MVA Testing - diffuse pattern (moderate-severe deficits in attention, executive function, processing speed c/w traumatic brain injury) MRI – subtle, diffuse changes in deep white matter

Additional History No loss of consciousness in MVA History of functional declines, sensory and motor changes in year prior to MVA Testing 1 year later shows further declines Neurologic examination shows abnormal nerve conduction consistent with multiple sclerosis

Errors in Formulation Keeping an Open Mind Acute onset word-finding deficits – no recent events History of worsening depression Neurologic exam normal Neuropsychological testing is normal except for severe impairment in confrontation naming with paraphasias Imaging shows multiple lesions, one in right temporal lobe with fresh blood

Additional History Left-handed Strong family history of left-handedness early strokes Findings consistent with hemorrhage of genetically-based, cavernous angioma (small tumor of vessel wall) in right, language dominant hemisphere Depression is irrelevant in this context

Errors in Formulation ‘Occam’s Razor’ 54 yo. M with recent memory complaints Neurologic exam normal Normal neuroimaging Family is concerned about ‘early Alzheimer’s’

Additional History Long-standing history of major depressive disorder No family history of dementia Trouble caring for home and finances after partner died 4 years ago Recently ‘got lost’ standing in front of his house, recovered quickly Continues to perform at high level at cognitively demanding job

Behavioral Geography of the Brain

The human brain has ~ 100 billion neurons in the human brain ~100 trillion synaptic connections ~3 million miles of axons in the human brain

Brain Orientation Anterior Posterior Superior Inferior Rostral Caudal Dorsal Ventral

Brain Orientation

Other definitions Lateral – to the side Medial (mesial) – toward the middle Proximal – areas of brain near to one another Distal – areas of the brain far from one another Ipsilateral – structures on same side of the body Contralateral – structures on opposite sides of body

Divisions of the Brain Major Division Subdivision Principal Structure Forebrain Telencephalon Cerebral Cortex Basal Ganglia Limbic System Diencephalon Thalamus Hypothalamus Midbrain Mesencephalon Tectum Tegmentum Hindbrain Metencephalon Cerebellum Pons Myelencephalon Medulla Oblongata Divisions of the Brain

Hindbrain Metencephalon Mylelencephalon Cerebellum Involved in aspects of learning and coordination of skilled or smooth movement Posture, walking, equilibrium Pons Links cerebellum to cerebrum, relays information from cerebral hemispheres to cerebellum Role in vision, balance, auditory processing Mylelencephalon Medulla Regulates bp, heart rate, respiration, controls breathing, basic muscle tone

Midbrain Mesencephalon Controls responses to sight Tectum (roof) Tegmentum (floor) Controls responses to sight Relay station of auditory and visual information Motor control of some muscles

Forebrain Diencephalon Telencephalon Thalamus hypothalamus Limbic System Basal Ganglia Cerebral Cortex

Diencephalon Hypothalamus Thalamus Controls aspects of motivated (pleasure and pain) and regulatory bx bodily functions, body temp, thirst, hunger circadian rhythms “master gland” – regulation and secretion of hormones Thalamus Gateway to cortex Relay center for sensory information Links nervous and endocrine system

Limbic system Groups of structures in center of brain above brainstem amygdala hippocampus parahippocampal gyrus cingulate gyrus fornix septum olfactory bulbs Maintains homeostasis Emotional reactions needed for survival

Basal Ganglia Collection of subcortical nuclei in forebrain Caudate nucleus Putamen Globus pallidus Structures involved in voluntary control of movement Motor planning and programming for speech Attention and alerting before a motor response

Cerebral Cortex

Blumenfeld, 2002

Brain anatomy

Brain anatomy