Neuroanatomy and Neuroimaging: Application to Alzheimer’s disease

diagnosisMegha Vasavada

Alzheimer’s disease

Most common form of dementia affecting 5.2 million Americans

Symptoms: problems with memory, thinking, and behavior

As the disease progresses the symptoms intensify› Disorientation› mood and behavior changes› deepening confusion about events, time and place › unfounded suspicions about family, friends and

professional caregivers› more serious memory loss and behavior changes› difficulty speaking, swallowing and walking.

Central Nervous System

Controls both voluntary activities and autonomic functions› Integrates sensory information, emotions,

thoughts, memory, and personality

Frontal Lobe

Temporal Lobe

BrainstemCerebellum

Occipital Lobe

Parietal Lobe

• 'higher' cognitive functions• attention• thought• voluntary movement• decision–making• language.

• recognition• perception (hearing, vision, smell)• understanding language• learning and memory

• perception/ integration of somatosensory information (e.g. touch, pressure, temperature, and pain)• visuospatial processing• spatial attention• spatial mapping• number representation

• maintaining homeostasis by controlling autonomic functions (blood pressure, breathing, digestion, heart rate, perspiration and temperature)•alertness•sleep•balance•startle response

• Vision

• coordination of voluntary movement• motor–learning• balance and posture• reflex memory•timing• sequence learning• integration of sensory information

http://www.g2conline.org/2022

Limbic Lobe

Limbic Lobe

• memory formation and storage• regulating emotion• processing smells

Frontal Lobe

Temporal Lobe

Occipital Lobe

Parietal Lobe

Brainstem

Cerebellum

Limbic Lobe

Magnetic Resonance Imaging

MRI:

• Visualize structural changes

• Track neuronal activation by studying blood flow (functional MRI)

Olfaction and Alzheimer’s

AD patients in the early stage have deficits in detection, recognition, and memory of an odor

AD patients have significantly reduced smell sensitivity

Areas involved in olfactory processing are the first areas affected by the classic pathology (Amyloid Beta plaques (Aβ) and neurofibrillary tangles (NFT))

Alzheimer’s Pathology Amyloid Beta

plaques › accumulation of Aβ in

extracellular space. Neurofibrillary

tangles › hyperphosphorylated

tau accumulation within neurons in the brain

Diagnosis occurs here

Alzheimer’s Pathology

Overview

Basic neuroanatomy› Medial temporal lobe = start of AD

patholgy› Olfactory areas are in the medial temporal

lobe Neuroimaging

› MRI provides a tool to look at the anatomy and activation in humans

Therefore, we will use MRI to study early changes in AD patients.

Hypothesis

Olfactory dysfunction will be present in our two patient groups

The volume of the primary olfactory cortex (POC) and hippocampus will be smaller in the two groups

The fMRI will show decreased activation in the POC and the hippocampus

Overall- fMRI is more sensitive to earlier changes in MCI and AD patients

Subjects

AD, mild cognitively impaired (MCI), and normal controls were enrolled› MCI- considered the transitional stage from

normal to AD (important group to study early diagnosis markers)

27 NC 21 MCI 15 AD

Methods

Smell test› University of Pennsylvania Smell

Identification Test MRI:

› Anatomical scan› fMRI scan with an olfactory task

Smell Test- Results

POC and Hippocampus are smaller in MCI and AD

Hip

pocam

pu

s

PO

C

Activation is drastically decreased in MCI and AD

Hippocampus

POC

CN MCI AD

Conclusion UPSIT scores:

› Smell function is affected in MCI and AD Volume

› hippocampus and POC in MCI and AD Activation

› in MCI and AD patients

Activation changes are more drastic than behavioral or volumetric

changes in the MCI group