Previous investigations have reported that most movement patterns in h
umans and other mammalian species are partitioned into 1-5-s units. Th
is finding has led to the hypothesis that a highly conservative physio
logical system, common among mammalian species, segments ongoing movem
ent patterns into 1-5-s 'chunks'. However, to date little or no work h
as been done to explore the physiological and neurochemical nature of
this segmenting phenomenon, therefore, it is unknown whether the same
evolutionarily conservative mechanism controls partitioning of all mov
ement patterns. The literature suggests that central dopamine plays a
key role in this 1-5-s partitioning. If this is so, then dopamine bloc
kers should result in significant alterations in the 1-5-s segmentatio
n of mammalian movement patterns. To test this hypothesis, the current
study determined whether the neuroleptic haloperidol significantly af
fected guinea pig chewing burst durations, which reportedly average 1-
3 s and are therefore considered to manifest this partitioning phenome
non. Seven male albino guinea pigs received daily 0.5 mg/kg i.m. halop
eridol injections, and three male albino guinea pigs received comparab
le saline injections (controls). After either 3 or 11 weeks, injection
s were stopped, and 1 week thereafter the animals were starved for 24
h and then videotaped singly in an experimental arena. Animals inevita
bly fed on alfalfa pellets during the taping session, and the chewing
bursts that occurred while the animals fed were timed. The results sho
wed that control animals' chewing bursts had durations similar to thos
e previously reported for free-roaming, non-drug-treated guinea pi,os.
However, haloperidol-treated guinea pigs' chewing bursts were signifi
cantly more variable in duration (p=0.0013) than those of matched cont
rol animals. Inspection of the data from individual animals revealed t
hat two haloperidol-treated animals had abnormally short chewing burst
durations, whereas three haloperidol-treated animals had abnormally l
ong chewing burst durations. The fact that haloperidol treatment was a
ssociated with either abnormally short or long chewing burst durations
is reminiscent of neuroleptic-induced human movement disorders, which
reportedly range from a 'paucity of movement' to 'perseverant movemen
ts'. This suggests that intact central dopaminergic systems may play a
n important role in modulating the duration of mammalian movement patt
erns, which normally ranges 0.2-5 s.