2. Pre-Programmed Reactions
Definition and origins of preprogrammed reactions
Elements of history
Sensory source ofpreprogrammed reactions
Complex nature ofpreprogrammed reactions
Examples of commonly studied preprogrammed
reactions
2
3. An unexpected perturbation of
a joint gives rise to a sequence
of EMG events in a stretched
muscle. The first one (M1)
comes at a short latency
(under 40 ms). Then two peaks
(M2 and M3) come at a latency
of between 50 and 100 ms. M2
and M3 are addressed as pre-
programmed reactions. Later,
a voluntary correction comes.
EMG
Time
Perturbation
M1
M2 M3
Voluntary
reaction
Definition Pre-Programmed Reactions
3
4. 4
Elements of history
PPR were first discovered in humans and only
later in animals
The first study Hammod(1954)
In particular, they have been studied in humans
during such tasks as maintaining a joint (limb)
posture, performing a quick joint movement,
walking, standing, gripping an object, and
speaking.
5. Pre-Programmed Reactions
Also called triggered reactions, M2–M3, functional
stretch reflex, transcortical reflex, long-loop reflex
Come at an intermediate latency (40–100 ms)
Are involuntary in nature but can be modified by
instruction
Can be triggered by stimuli of virtually any modality
Generate a quick, crude compensation for the
perturbation
Are followed by voluntary corrections
5
8. Pre-programmed reactions
demonstrate a strong
dependence on the instruction.
If the subject is instructed to
resist perturbations, the pre-
programmed reactions are large
(solid lines). If the subject is
asked to let the limb move,
the pre-programmed reactions
are much smaller (dashed lines).
Note that the M1 reaction is the
same.
Effect of Instruction on Muscle
Reactions to a Perturbation
EMG
Time
Perturbation
M1
M2 M3
Voluntary
reaction
React
Let go
8
10. A subject is holding a position in a
joint against a load with a central
command to a muscle. If the subject
knows that a perturbation can
occur, he/she can prepare an
addition to the central command
that would compensate for the
predicted perturbation. The pre-
programmed command ( C) is∆
triggered by peripheral signals
generated by the perturbation and
attenuates the mechanical effects of
the perturbation.
A Possible Scheme
Muscle
Central command
Tonic stretch reflex
mechanism
∆C
Afferents
10
11. The actual source of the
triggering signal for a
pre-programmed
reaction is not important
as long as the signal
carries sufficient
information. It can be
provided by
proprioceptors, a flash of
light, a loud tone, etc.
Pre-Programmed Responses Can Be
Triggered by Any Sensory Signal
Muscle
Central
command
Tonic stretch reflex
mechanism
∆C
Proprioceptors
Vision
Hearing
11
12. If a perturbation occurs
during a fast voluntary
movement, EMG changes are
seen at a characteristic for the
pre-programmed reactions
latency. Generally, they
involve an increase in the
activity of a muscle that acts
against the perturbation, and
a decrease in the activity of a
muscle that is assisted by the
perturbation (bold lines).
Effects of a Perturbation Applied
During a Fast Movement
agonist
antagonist
time
EMG
an increase
in load
12
13. Muscle vibration has
different effects on
different components of
the responses to an
external perturbation.
The early response (M1) is
suppressed just like the H-
reflex, whereas the pre-
programmed response
(M2-M3) is unchanged.
Effects of Vibration on M1-2-3
Responses
Vibration
EMG
TimePerturbation
M1 M2-M3
13
14. Examples of commonly studied
preprogrammed reactions
1) Classical (lab conditions)
2) Grip Reactions
3) postural perturbations (ankle and hip
strategies)
4) Preprogrammed Reactions in Locomotion
“Corrective stumbling reaction”
14
15. 15
One ofthe most commonly used methods to
study preprogrammed reactions is to ask a
subject to hold a position in a joint against a
bias extemalload and then to change the
load quickly.
Classical (lab conditions)
16. Pre-programmed postural
corrections to a perturbation
created by platform movement
are context-dependent. If the
cup is loaded with play dough,
the corrections will be
different than if the cup is full
of hot tea.
Effects of Intention
on Quick Muscle Reactions
16
Grip reaction
17. mechanical or electrical
stimulation of the paw
during locomotion induces
different reactions in the
swing and the stance phases.
In the swing phase (A), there
is a flexor reaction, so that
the leg steps over a fictitious
obstacle. In the stance phase
(B), there is an extensor
reaction, leading to the
shortening of the stance
phase for this limbA.
Corrective Stumbling Reaction
Surface
Stim
Stim
A B
17
18. Corrective stumbling reaction:
Preprogrammed Reactions
in Locomotion
18
Occurs during locomotion
Can be induced by a
mechanical stimulus to the
foot
Represents a complex pattern
of EMG changes
Leads to a quick step over the
obstacle
22. Thank you for your attention
22
Stop judging others in order to
meet composureDeepak Chopra
Editor's Notes
نباید رفلکس کششی را با واکنش پیش برنامه ریزی شده اشتباهی بگیریم ؟؟؟؟؟؟ 1- پ پ ر هم تحت انقباض و هم کشش فعال می شوند ولی رفلکس کششی فقط نسبت به کشش و تون عضله حساس است
. 2-
Consider the following scheme for the generation of preprogrammed reactions (figure 12.3). The instruction to keep a joint position against a load requires the subject to generate a voluntary command to muscles controlling this joint. If the subject knows that a perturbation can occur, a corrective command can be prepared in advance and is ready to be triggered by an appropriate peripheral signal.
Note that this scheme implies preparation of a preprogrammed reaction by some "higher" electer, for example the cortex, while the loop of the reaction may not involve the "higher" centers.
هنگام اشفتگی ناگهانی در یک حرکت سریع ارادی تغیراتی هم در پ پ ر بوجود می آید که به قرار زیر می باشد . افزایش EMG درعضله مخالف اغتشاش و کاهش EMG در عضله مخالف اغتشاش
تغییرات لرزش ناشی از فعالیت آوران عضله تاثیری بر PPRندارند ولی باعث کاهش یا سرکوب فعالیت M1 می شود . چرا ؟؟؟؟؟؟؟؟؟؟؟؟
مثال رایج از واکنش پیش برنامه ریزی شده در محیط آزمایشگاهی اینکه نگه داشتن بازو یا دست در مقابل یک اغتشاش بیرونی
