The responses o f f iv e d if fe r e n t p re p a ra tio n s t o a range o f fre q u e n c ie s o f between 1-50Hz. a re ill u s t r a t e d i n ( F ig . 3 ) . T y p ic a l e x tr a c e llu la r re c o rd in g s a t d if f e r e n t fre q u e n c ie s shew two d is t in c t p a tte rn s o f response (F ig .3 a & b ) . F re q ue n cie s o f v ib r a t io n o f 1-20Hz. in c lu s iv e produced t y p ic a l p a tte rn s o f response ( F ig .3 a ) . The response i s c h a ra c te riz e d by th e presence o f numerous sm a ll a m p litu d e s p ik e s (1 0 -1 5 p v ), few s p ik e s above 35pv and th e absence o f sp ike b u rs ts . T h is ty p e o f response i s s im ila r to re c o rd in g s made d u rin g th e la t e r a l fle x u r e o f th e u n re s tra in e d arm t i p . At fre q u e n c ie s above 20Hz. th e p a tte rn o f re co rd ed response c o n s is te d o f a complex i n i t i a l b u rs t o f s in g le u n it a c t i v i t y and th e r e a fte r d is c re te b u rs ts o f sp ik e s th e la r g e s t between 40-45pv ( F ig .3 b ) . The p a tte rn o f response was s im ila r to those re co rd ed to a shadow s tim u lu s .
FIG. 3 .
Graph showing th e ty p ic a l responses i n term s o f t o t a l number o f re co rd e d s p ik e s o f f iv e
in d iv id u a l a n im a ls o u t o f 25 p re p a ra tio n s t o a range o f fre q u e n c ie s o f v ib r a t io n . ( 1 -5 0 H z). a) E x t r a c e llu la r re c o rd in g fro m th e R.N .C , in response to fre q u e n c ie s o f v ib r a t io n o f between 1 and 20Hz. b) E x tr a c e llu la r re c o rd in g fro m th e R.N.C. in response to fre q u e n c ie s o f v ib r a t io n o f above 20Hz. Note th e two d if f e r e n t p a tte rn s o f response. The lo w e r arrow in d ic a te s th e
120- 100- (/) 40 I--- 20-
20
10
3 0 4 0 50Hz.
a
1s
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Hydrodynamjo P is tu rb a n Qe s t im u li.
The mov«nent o f th e perspex ro d and subsequent wave w hich passed a cro ss th e t i p o f th e arm r e s u lte d i n a b u rs t o f sp ike s re co rd e d e x tr a c e llu la ly from th e r a d ia l nerve co rd . Eadi response c o n s is te d o f a v a r ia b le number o f u n its between 10~45pv. dependant upon s tim u lu s . In c re a s in g th e m agnitude o f th e p re ssure wave e lic it e d a co rre sp o n d in g in c re a s e i n th e s iz e and number o f u n it p o te n tia ls w it h in th e re co rd e d response ( F ig . 4 ) . The i n i t i a l b u rs t o f s p ik e s i n th e p a tte rn became more complex w ith in c re a s in g m agnitude and re g u la r sp ike b u rs ts were e v id e n t. Ih e g re a te r m agnitude waves re s u lte d in a p a tte r n o f response th a t i s s im ila r to th e shadow response. In c re a s in g th e r a te a t w hich the p re ssu re wave moved a c ro s s th e arm t i p re s u lte d i n an in c re a s e in th e s iz e o f re c o rd a b le s p ik e , b u t a decrease i n th e number o f s m a lle r s p ik e s w it h in th e response ( F ig . 5 ) . The la r g e s t sp ike measured around 40pv. No response was e l ic it e d fro m th e R.N.C. to movement o f th e waves o f aqy m agnitude once th e sp in e s had been removed ( F ig . 6 ) . The shadow response co u ld s t i l l be reco rd ed however in d ic a tin g t h a t th e s u c tio n e le c tro d e rem ained a tta c h e d to th e R.N.C. subsequent to th e rem oval o f th e s p in e s and th e nervous system rem ained fu n c tio n in g . T h is a ls o in d ic a te s th a t th e shadow response i s n o t w h o lly a s s o c ia te d w ith th e sp in e s.
FIG. 4 .
E x t r a c e llu la r re c o rd in g s fro m th e R.N .C . in response to s in g le waves o f in c re a s in g m agnitude p a ssin g a c ro s s th e t i p o f a s in g le arm ^
p re p a ra tio n . The d isp la ce m e n t o f a) 19cjm .
b) 39can^ . c) 78cm^ . d) 98cm^ . o f w a te r o ver a 0 .5 second p e rio d produces th e waves o f
in c re a s in g m a g n itu d e . The lo w e r tra c e in d ic a te s th e moment o f a p p lic a tio n o f th e s tim u lu s .
cr
o
FIG . 5 .
E x t r a c e llu la r re c o rd in g s i n response to s in g le waves p a ssin g a c ro s s th e arm t i p a t in c re a s in g r a te s , a) 3mm. s e ^ ' . b) 12mm. sec” . c) 20mm.sec . d) 30mm.sec” . The lo w e r tra c e in d ic a te s th e moment o f a p p lic a tio n o f th e
D )
O
w
FIG. 6 .
a) Responses re co rd e d e x t r a c e llu la r ly in response to th e re p ea ted d isp la ce m e n t o f 78mm o f w a te r i n a 0 .5 second p e rio d t o produce s in g le waves r e s u lte d i n a complex t r a i n o f s in g le u n it a c t i v it y from an in t a c t s in g le arm p re p a ra tio n , b) Same s t im u li p re se n te d to th e s in g le arm p re p a ra tio n a f t e r th e arm s p in e s have been
removed, r e s u lte d in no re c o rd a b le a c t i v it y from th e R .N.C. c) The shadow response re co rd e d frcm th e p re p a ra tio n w ith th e sp in e s removed in d ic a te th a t a b la tio n o f th e arm sp in e s had n o t a ffe c te d th e a b i l i t y to re c o rd responses fro m th e R.N.C. The I w e r tra c e i n a) and b) and th e arrow in c) in d ic a te th e i n i t i a t i o n o f th e s t im u li.
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Mov_ement Q L In d iv id u a l .Spine.g.»
The movement o f a s in g le la t e r a l sp in e produced a response in th e form o f a number o f s in g le u n it p o te n tia ls t h a t were re c o rd a b le from th e R.N .C . o f th e b r i t t l e s t a r . B oth th e number and th e a m p litu d e o f re co rd e d s p ik e s in c re a s e d as th e ang le th ro u g h which th e sp in e was moved in c re a s e d ( F ig . 7 ) . The movement o f a sp in e 10*^ r e la t iv e to i t s i n i t i a l p o s itio n re s u lte d in a s in g le p o te n tia l b e in g re co rd e d (a m p litu d e 15pv) w h ils t movement th ro u g h an a n g le o f 2 5° produced a complex b u r s t, re c o rd a b le fro m th e nervous qrstem w ith th e la r g e s t u n it a p p ro x im a te ly 45pv. In c re a s in g th e ra te a t w h ich a s in g le spine was moved th ro u g h a g iv e n a n g le e lic it e d a co rre s p o n d in g in c re a s e i n th e re c o rd a b le response in te rm s o f b o th number and a m p litu d e o f u n it (F ig .8 a ,b , c ) . In a l l th e re c o rd in g s th e re was an o bvious la g p e rio d between th e onset o f th e s tim u lu s and th e re co rd e d re sp on se . The d u ra tio n o f t h i s la g p e rio d was dependant upon th e ra te a t w hich th e s p in e was moved. The f a s t e r th e spine was moved, th e la r g e r th e reco rd ed p o t e n tia l and th e g re a te r th e decrease i n th e tim e between s tim u lu s and re co rd ed response. T h is suggests t h a t th e la r g e r d ia m ete r neurones from w hich th e sp ike s a re re co rd e d may have a g re a te r c o n d u c tio n r a te th a n th e s m a lle r neurones. F u rth e r expe rim en ts were c a r r ie d o u t w here two in d iv id u a l la t e r a l sp in e s, on a d ja c e n t segments were moved s im u lta n e o u s ly . In c re a s in g th e r a te a t w hich
FIG. 7 . E x t r a c e llu la r re c o rd in g s from th e R.N .C . in response to th e mdvanent o f in d iv id u a l la t e r a l s p in e s , th ro u g h a n g le s o f a) 10° . b ) 15° . c) 20° . d) 25° . r e la t iv e to t h e ir i n i t i a l p o s itio n ly in g f l a t a g a in s t th e arm o f th e
a n im a l. The lo w e r tra c e in d ic a te s th e moment a t w hich th e s p in e s were moved.
cr
FIG. 8
Responses re co rd e d t o th e movement o f in d iv id u a l s p in e s a t in c re a s in g ra te s o f a) 1 second, b) 0.6 second, c) 0.1 seconds th ro u g h an a n g le o f 20° measured r e la t iv e to t h e ir i n i t i a l p o s itio n , d ) , e) and f ) a re th e re co rd e d resp on se s to th e sim u lta n e o u s movaaents o f two a d ja c e n t sp in es a t th e same r a te s . The second response in each re c o rd i s th e movement o f th e s p in e s back to t h e ir o r ig in a l p o s itio n s . The lo w e r tra c e s in d ic a te th e p o in ts a t w hich th e sp in e s w ere moved.
CD
O
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( F ig .8 d ,e , f ) e lic it e d n o t o n ly a c o rre s p o n d in g in c re a s e i n response w ith r a te , b u t an in c re a s e in th e response
when compared to movement o f a s in g le s p in e a t
c o rre s p o n d in g ra te s . A s im ila r b u rs t o f sp ik e s was re co rd e d when th e s p in e s w ere moved back t o t h e ir o r ig in a l p o s itio n s ly in g f l a t a g a in s t th e s u rfa c e o f th e arm.
The same e xp e rim e n ts w ere c a rrie d o u t on s in g le arm p re p a ra tio n s where a l l s u rfa c e s tru c tu re s and e p ith e liu m