The startle response provides the substrate for the commonest expression of generalized myoclonus. Sudden or unexpected visual, auditory, somatosensory, and vestibular stimuli elicit the startle response. The response may be augmented if these stimuli are accompanied by fright (1). The startle response consists of two components. The initial short latency component is a stereotyped reflex comprising a blink, a facial grimace, and brisk flexion of the neck, trunk, and upper limbs (2). Occasionally, limb extension is involved. The duration of this component is short and the responses habituate with repeated stimulation. The secondary component of the startle response occurs at a longer latency and is more variable in appearance and duration (1,3). The clinical manifestations of the secondary component are determined by the nature of the startling stimulus and the situation in which it occurs. This component is influenced by the state of arousal and attention (4). Accordingly, it contains emotional and voluntary behavioral responses to the startling stimulus. This part of the startle response has been described as an “orientating” response (3) in preparation for action towards the stimulus. The electrophysiologic characteristics of the second component of the startle response are less well-defined.

There are a number of clinical abnormalities of the startle reflex. These include pathologic enhancement of the earliest component of the reflex in familial hyperekplexia or startle disease (4,5), due to mutations of the glycine receptor gene (GLRA1) (6), and symptomatic hyperekplexia due to lesions in the region of the nucleus pontis caudalis of the brainstem reticular formation (2,7). Conversely, degeneration of this area of the brainstem in Steele-Richardson-Olszewski syndrome (8) results in loss of the early component of the startle response.

Exaggeration of startle responses have long been described in latah (9,10), Jumping Frenchmen of Maine (11,12), and related conditions referred to as “culture-bound startle syndromes” (13,14). More recently, exaggerated startle responses have been described in drug withdrawal, Tourette syndrome (15), and psychiatric conditions such as post-traumatic stress disorder (4,14). The nature of the startle response in the culture-bound startle syndromes will be considered further in this review.

Latah was described by the British adventurer H.A. O’Brien in 1884 during his travels through the Malay Peninsula (9). The word “latah” refers to a nervous or ticklish disposition. In an eloquent account of the behavior of latah sufferers, O’Brien noted that it encompassed a degree of subservience, foreshadowing the importance of behavioral aspects of latah, particularly forced obedience. He declined to record the full expression of the behavioral aspects that have been detailed in more recent descriptions (10,13). In an attempt to put latah into some perspective today, it is helpful to review the original descriptions. The latah sufferer exhibited a prominent “start” in response to sound or a frightening stimulus. This was accompanied by a tendency to strike out at nearby persons and vocalizations with coprolalia. They appeared nervous and, in addition to the startle, were seemingly compelled to act in an impulsive manner in response to external stimuli. Words such as “tiger,” “alligator” or “snake,” particularly when shouted, evoked in “latahs” an exaggerated and fearful response such as cowering or behaviour such as jumping off a boat into the river. More complex behaviors were observed, including echolalia, echopraxia, and imitation behavior. O’Brien described imitation behavior in a man who copied O’Brien’s waving and whistling, a woman who took off her clothes (despite his protestations) after a man removed his coat, and a cook on a river steamer who tossed a child in the air, then dropped the child, in response to a sailor performing the same actions with a piece of wood.

Many papers addressed the subject of latah over the next 100 years. All drew attention to the combination of a startle response and a variety of complex behaviors, especially echophenomena, vocalizations and coprolalia, and forced obedience. In the most recent article, Tanner and Chamberland presented a video demonstrating each of these behaviors in Indonesian Malays and concluded that the clinical picture had changed little since the original description (16).

At around the same time as O’Brien’s description, George Beard reported his observations on the Jumping Frenchmen of Maine (11). These were French Canadian lumberjacks from adjacent Quebec who lived and worked in remote, isolated communities near Moosehead Lake in northwestern Maine. Beard’s descriptions emphasize the behavioral aspects of the phenomenon, such as forced obedience and echolalia, as much as, if not more than, an exaggerated startle response (11). The social dimensions of the jumpers’ behavior was also emphasized, and they appear to have been the source of entertainment. Beard observed, “When told to strike, he strikes, when told to throw it, he throws it, whatever he has in his hands.” He examined echolalia by reciting Latin text (with which the lumberjacks would not have been familiar):

…and he repeated or echoed the sound of the word as it came to him, in a quick sharp voice, at the same time he jumped, or struck, or threw, or raised his shoulders, or made some other violent muscular motion. They could not help repeating the word or sound that came from the person that ordered them any more than they could help striking, dropping, throwing, jumping or starting; all of these phenomena were indeed but parts of the general condition known as jumping (11).

Some of the behaviors observed in the lumberjacks, such as throwing knives, striking hot stoves, or jumping into fire or water, were potentially dangerous or injurious, further adding to the intrigue of the condition.

The jumpers were mainly men who were otherwise healthy. Beard emphasized the condition could be familial and begin in childhood. Subsequent reports of similar cases, all of French Canadian descent, shed little further light on this behavioral complex beyond the notion of a culturally determined and learned behavior as originally suggested by Beard (11). The recent examination of a small group of eight jumpers in the Beauce region of Quebec led to the conclusion that they exhibited situational behavior related to an isolated existence in a remote community, and that the phenomenon had diminished with the passage of time (12,17). Similar features were described in presumed descendants of the French Acadians from Nova Scotia, the “Ragin’ Cajuns” of Louisiana (18), and others (19) who were possibly genetically related to the Jumping Frenchmen of Maine. Startle behavior was also described in other population groups (20).