Stress is defined as a state that is induced by a challenge to homeostasis, survival, and/or reproduction. This challenge typically comes in the form of a stressor. This stressor may be real (for example, someone threatening you,) or imagined (something you are deathly afraid of that is not intrinsically harmful, like a mouse or public speaking).  Anxiety is an emotional and subjective response to stress. Anxiety is also a signal of the internal manifestation of an external stimulus or event.

Anxiety prepares you for action. It gears you up to face a threatening situation. It can also improve your performance; you might be motivated by anxiety to study harder for an exam, or be more on your toes when you're making a speech. In general, some level of anxiety help you perform better. However, too much anxiety can definitely be a bad thing.

At the level of an anxiety disorder, this normally helpful emotion can do just the opposite – it can prevent you from acting (i.e., avoiding public speaking), or it can decrease your ability to perform (you fail an exam because you were “too nervous”). At its most extreme, anxiety can disrupt everyday daily life and even seemingly “normal” activities.

Persons suffering from anxiety disorders seek treatment for:
Sustained autonomic arousal (e.g. dizziness, pounding heart, stomach pains) Physical symptoms (e.g. restlessness, headaches, chest pain, difficulty breathing)
Psychological symptoms (e.g. feelings of dread, fear, panic, nervousness, irritability, inability to concentrate, make decisions), *POOR CONCENTRATION*)

The Yerkes-Dodson law is widely used to explain the relationship between state of anxiety or arousal and her/his ability to effectively perform a cognitive task. The inverted U-shaped relationship graphically shows the continuum between “good” stress (anxiety levels that help us perform better) and “bad” stress (anxiety levels that are counterproductive to performance).

The way in which stressors affect cognitive functioning is the major focus of Dr. Echevarria’s research.  Stress-mediated alterations in cognitive processes are explored via both human and animal models. Converging evidence suggests that stressors can produce narrowing of or even lapses in attention. The speed with which decisions are made can also be influenced. Stress-related anxiety has also been shown to impair processes in the hippocampus that are understood to be involved in memory. One mechanism by which memory impairment may occur is neurochemical. During periods of stress several neuroactive chemicals are released into the bloodstream. Low to moderate levels of glucocorticoids and catecholamines can facilitate memory function, while higher levels can lead to the disruption of cognitive processes. It is these very neuroactive chemicals, along with correspondence from related brain areas that potentially provide the physical correlates to the inverted U-shaped function that plots the continuum between stress-responding and performance.