Related Experiment Video
Updated: Jul 10, 2026

Examining the Characteristics of Episodic Memory using Event-related Potentials in Patients with Alzheimer's Disease
Published on: August 30, 2011
Cognitive deficit induced by acute tryptophan depletion in patients with Alzheimer's disease
R J Porter1, B S Lunn, L L Walker
1Academic Department of Psychiatry, University of Newcastle upon Tyne, England.
Objective:
The study assessed the effects on global cognitive function and mood of a reduction of brain serotonin by means of acute tryptophan depletion in 16 patients with dementia of the Alzheimer type and in 16 cognitively intact comparison subjects.
Method:
In a double-blind, crossover design, subjects received a tryptophan-free amino acid drink to induce acute tryptophan depletion and, on a separate occasion, a placebo drink containing a balanced mixture of amino acids. On each occasion, ratings of depressed mood were made at baseline and 4 and 7 hours later, and the Modified Mini-Mental State was administered at baseline and 4 hours later.
Results:
Patients with dementia of the Alzheimer type had a significantly lower mean score on the Modified Mini-Mental State after acute tryptophan depletion than after receiving placebo. The comparison group showed no difference in mean score on the Modified Mini-Mental State after acute tryptophan depletion and after receiving placebo. No significant changes in mood were found in either group.
Conclusions:
Acute tryptophan depletion significantly impaired cognitive function in patients with dementia of the Alzheimer type. Compromised serotonergic function, in combination with cholinergic deficit, may make an important contribution to cognitive decline in dementia of the Alzheimer type.
Related Concept Videos
Alzheimer's Disease: Overview
The clinical diagnosis of AD hinges on the presence of memory and other cognitive impairments. Biomarkers, such as changes in Aβ and tau...
Alzheimer's Disease: Treatment
Role of Neurotransmitters in Memory
Glutamate and Synaptic Plasticity
Glutamate, the brain's main excitatory neurotransmitter, is critical for...
Alzheimer Disease l: Introduction
Alzheimer Disease ll: Pathophysiology
Dementia l: Introduction

