The cerebellar dorsal granular ridge in an elasmobranch has proprioceptive and electroreceptive representations and projects homotopically to the medullary electrosensory nucleus

1. Response properties of neurons in the dorsal granular ridge (DGR) of the little skate, Raja erinacea, were studied in decerebrate, curarized fish. Sensory responses included proprioceptive (426 of 952; 45%) and electroreceptive units (526 of 952; 55%). Electroreceptive units responded to weak electric fields with a higher threshold than lower-order units and had large ipsilateral receptive fields, whose exact boundaries were often unclear but contained smaller, identifiable best areas. Proprioceptive units responded to displacement of the ipsilateral fin and were either position-or movement-sensitive.
2. Both proprioceptive and electroreceptive units showed a progression of receptive fields from anterior to posterior body in the rostral to caudal direction along the length of DGR. Sensory maps in DGR projected homotopically to the electrosensory somatotopy in the dorsal nucleus. Peak evoked potentials and units responding to local DGR stimulation occurred only in areas of the dorsal nucleus with receptive fields located within the composite receptive field at the DGR stimulation site.
3. Single shocks to DGR produced a short spike train followed by a prolonged suppression period in the medullary dorsal nucleus. These results have implications for the role of the parallel fiber system in medullary electrosensory processing.

     

The role of amino acid neurotransmitters in the descending control of electroreception

The roles of amino acid neurotransmitters in determining the processing characteristics of the electrosensory lateral line lobe (ELL) in Apteronotus leptorhynchus were investigated by studying the responses of ELL output neurons to pressure ejection of various neurotransmitter agonists and antagonists alone and in combination with simple electrosensory stimuli.

1. Pressure ejection of L-glutamate into the ELL dorsal molecular layer caused either excitation or inhibition of ELL efferent neurons (pyramidal cells). The sign of these responses reversed with changes in the position of the pressure pipette. Histological verification of drug ejection sites relative to recorded cells and diffusion estimates indicate that excitatory and inhibitory responses result from glutamate activation of pyramidal cells and of inhibitory interneurons, respectively.
2. ELL output cells respond to both NMDA and non-NMDA glutamate agonists and the responses are attenuated by co-ejection of specific antagonists indicating that both AMPA/kainate and NMDA receptors exist on pyramidal cell apical dendrites.
3. Gamma-aminobutyric acid inhibits basilar and nonbasilar pyramidal cells when ejected near their apical dendrites and disinhibits them when ejected near surrounding inhibitory interneurons confirming the presence of GABA receptors on these cell types.
4. An NMDA antagonist did not alter pyramidal cell responses to electrosensory stimuli but a non-NMDA antagonist altered both responses to the stimuli and firing frequency shortly following stimulus cessation.

     

Selective phonotaxis to advertisement calls in the gray treefrog Hyla versicolor: behavioral experiments and neurophysiological correlates

1. The significance of particular acoustic properties of advertisement calls for selective phonotaxis by the gray treefrog, Hyla versicolor (= HV), was studied behaviorally and neurophysiologically. Most stimuli were played back at 85 dB SPL, a level typically measured at 1–2 m from a calling male.
2. Females preferred stimuli with conspecific pulse shapes at 20° and 24°C, but not at 16°C. Tests with normal and time-reversed pulses indicated the preferences were not influenced by the minor differences in the long-term spectra of pulses of different shape.
3. Pulse shape and rate had synergistic or antagonistic effects on female preferences depending on whether the values of one or both of these properties in alternative stimuli were typical of those in HV or heterospecific (H. chrysoscelis = HC) calls.
4. More auditory neurons in the torus semicircularis were temporally selective to synthetic calls (90%) than to sinusoidally AM tones and noise (< 70%).
5. Band-pass neurons were tuned to AM rates of 15–60 Hz. Neurons were more likely to be tuned to HV AM rates ( < 40 Hz) when stimuli had pulses with HV rather than HC shapes.
6. Sharp temporal tuning was uncommon and found only in neurons with band-pass or low-pass characteristics.
7. Many neurons differed significantly in response to HV and HC stimulus sets. Maximum spike rate was more often elicited by an HV stimulus (74%) than by an HC stimulus (24%).
8. Differences in spike rates elicited by HV and HC stimuli were attributable to combinations of differences in the rise times and shapes of the pulses.

     

Modulation of swimming in Tritonia: excitatory and inhibitory effects of serotonin

1. In the mollusc Tritonia escape swimming is produced by a network of central pattern generator (CPG) neurons. The purpose of this study was to determine which neurotransmitters might be involved in the swim system.
2. Injection of serotonin (5HT) into whole animals elicited swimming followed by a long-lasting inhibition of swimming. In isolated brain preparations, bath-applied 5HT elicited a swim pattern at short latency and also caused a long-lasting inhibition of the swim pattern. The activation of swimming by 5HT was associated with a tonic depolarization of cerebral cell 2 (C2) and the dorsal swim interneurons (DSI) which form part of the swim CPG network.
3. In isolated brain preparations, bath applied glycine, histamine, proctolin, and FMFRamide had no effect on the swim motor pattern elicited by electrical stimulation of a peripheral nerve. Aspartate, carbacol, dopamine, glutamate, octopamine, pilocarpine, and small cardioactive peptide-B (SCP_B) inhibited the activation of swimming by nerve stimulation.
4. The 5HT antagonists cyproheptidine, tryptamine, and 7-methyltryptamine had no effect on swimming, but methysergide and fenfluramine inhibited swimming to both normal sensory stimuli and exogenously applied 5HT.
5. Staining with a polyclonal antibody indicated that one class of CPG neurons, the dorsal swim interneurons (DSI), was immunoreactive for 5HT.
6. Taken together, the data suggest that pattern generator interneurons, particularly the DSIs, use 5HT as a neurotransmitter.

     

Quantitative assessment of song-selectivity in the zebra finch “high vocal center”

1. Auditory responses in the zebra finch (Taenopygia guttata) song-system nucleus HVc were assessed at 54 recording sites by 3 different methods: discriminated action potentials; excitatory summed responses; and excitatory minus inhibitory summed responses. Four standard stimuli were presented at each site: the bird's own song; this song reversed; a conspecific song; and a noise burst. Responses were quantified by calculating a relative response index that partitioned the response, to provide a response profile, across the stimuli.
2. Regardless of analysis method, the strongest response was most often to the bird's own song (78–82%, depending on method). The predominant rank order of response strength across the remaining three stimuli was conspecific song > reversed song > noise.
3. The distribution of relative response magnitude was sensitive to analysis method. Discriminated spikes captured the heterogeneity of HVc neurons, whereas the excitatory summed responses reflected the overall trends more consistently. When inhibition was subtracted from excitation in the summed responses, the variance of the relative responses increased, but this method presented some problems for statistical analysis.
4. A small sample of neurons in other forebrain auditory areas was used for comparative analyses. At these recording sites, the bird's own song did not consistently elicit the best response and there were generally smaller differences in the relative responses to the four stimuli. The smaller degree of stimulus selectivity among these cells resulted in less sensitivity to differences in the assessment methods.

     

Temporal discharge patterns of tectal and medullary neurons chronically recorded during snapping toward prey in toads Bufo bufo spinosus

In freely moving toads, the temporal discharge patterns of tectal and medullary neurons were observed during prey-catching.

1. Tectal T5.2 and T8.1 neurons displayed a premotor warming up firing that in the former was addressed specifically to prey orienting or snapping and in the latter generally to almost any kind of body movement.
2. The temporal discharge patterns of T5.2 neurons during snapping were different from those during orienting toward prey. Snapping started in the peak phase of warming up; firing was immediately terminated during the snap; thereafter some rebound activity was observed. Orienting started after the premotor warming up in the declining phase whilst the neuron kept on firing during orienting and then settled when the orienting movement was completed.
3. In toads which were not motivated to catch prey — comparabl to immobilized ones — the discharge frequency of T5.2 neurons toward a prey stimulus revealed no such warming up.
4. Because it is known that prey-selective T5.2 neurons are controlled by pretectal inhibitory influences, the following experiment was conducted: during recording a T5.2 neuron a pretectal lesion was applied ipsilaterally to the recording site. After a few seconds, the neuron showed a strong premotor wanning up in response to any kind of moving object, followed by prey-catching.
5. In the medulla oblongata, different H-type neurons of the hypoglossal nucleus displayed specific discharge patterns which resembled the tongue protractor and retractor muscle activities; a third type resembled the activity of the genio/sterno-hyoid muscle, which are suggested to stabilize the hyoid bone during snapping.
6. There were medullary M8-type neurons with properties similar to T8.1.
7. Snapping could be triggered by electrical stimulation of the optic tectum in the representation of the frontal visual field, but not by stimulation in the hypoglossal nucleus or the adjacent medial reticular formation.
8. A concept of a neuronal circuit for the coordination of tongue muscle contractions in response to prey is proposed.

     

Medullary electrosensory processing in the little skate

1. Previous studies have demonstrated that the resting activity of electrosensory ALLN fibers is modulated by the animal's own respiratory activity and that all fibers innervating a single ampullary cluster are modulated with the same amplitude and phase relationship to ventilation. We demonstrate that ALLN fibers in the skate are modulated in this common-mode manner bilaterally, regardless of receptor group, orientation, or position of the receptor pore on the body surface (Fig. 2). 2. Ascending efferent neurons (AENs), which project to the electrosensory midbrain from the DON, are modulated through a much smaller portion of their dynamic range. AENs give larger responses to an extrinsic local electric field than to the respiratory driving, indicating that a mechanism exists for suppressing ventilatory electrosensory reafference. 3. In paralyzed animals no modulation of resting activity or of responses of extrinsic electric fields could be observed with respect to the animal's respiratory motor commands in the absence of electrosensory reafference. 4. Cells of the dorsal granular ridge (DGR) project to medullary AENs via the DON molecular layer. A majority of proprioceptive DGR neurons are modulated by ventilatory activity, however, in a given fish the modulation is not in the same phase relationship to ventilation among DGR units. 5. The modulation of AENs during respiration was increased following transection of the contralateral ALLN (Fig. 9). Resting activity and responses to excitatory stimuli were inhibited by simultaneous stimulation of the transected contralateral ALLN indicating that a common-mode rejection mechanism is mediated via the commissural interconnections of the DONs.     

Response characteristics of wide-field non-habituating non-directional motion detecting neurons in the optic lobe of the locust,Locusta migratoria

1. Extracellular recordings from wide-field nonhabituating non-directional (ND) motion detecting neurons in the second optic chiasma of the locust Locusta migratoria are presented. The responses to various types of stepwise moving spot and bar stimuli were monitored (Fig. 1)
2. Stepwise motion in all directions elicited bursts of spikes. The response is inhibited at stimulus velocities above 5°/s. At velocities above 10°/s the ND neurons are slightly more sensitive to motion in the horizontal direction than to motion in the vertical direction (Fig. 2). The ND cells have a preference for small moving stimuli (Fig. 3).
3. The motion response has two peaks. The latency of the second peak depends on stimulus size and stimulus velocity. Increasing the height from 0.1 to 23.5° of a 5°/s moving bar results in a lowering of this latency time from 176 to 130 ms (Fig. 4). When the velocity from a single 0.1° spot is increased from 1 to 16°/s, the latency decreases from 282 to 180 ms (Figs. 5–6).
4. A change-of-direction sensitivity is displayed. Stepwise motion in one particular direction produces a continuous burst of spike discharges. Reversal or change in direction leads to an inhibition of the response (Fig. 7).
5. It shows that non-directional motion perception of the wide-field ND cells can simply be explained by combining self-and lateral inhibition.

     

Encoding of plant odours by receptor neurons in the pine weevil (Hylobius abietis) studied by linked gas chromatography-electrophysiology

Receptor neuron responses to plant volatiles, trapped by head-space procedures, were examined in the pine weevil Hylobius abietis, using gas chromatography linked with electrophysiological recordings from single neurons. Seventy-two receptor neurons were tested 173 times for various plant volatile mixtures, either via a polar or a non-polar column.

1. All responses appeared as increased firing rates which followed the concentration profiles of the GC-eluted compounds.
2. The neurons were classified separately for the two column types in 17 and 19 groups respectively, according to the compounds they responded to. It suggests that the plant odour information is encoded by a large, but limited number of receptor neuron types.
3. Most neurons responded to a limited number of compounds (1–5) and showed a marked best response to one of them, whereas additional responses to several other components which seems to be structurally similar, was recorded for some neurons. It suggests that the plant odour receptor neurons are rather narrowly than broadly tuned, and that each neuron is specialized for receiving information about one or a few related compounds.
4. Most neurons responded to monoterpenes, whereas the other neurons responded to compounds of other categories.
5. Both major and minor plant volatile components activated specifically receptor neurons.

     

Medullary electrosensory processing in the little skate

1. Ampullary electroreceptors in elasmobranchs are innervated by fibers of the ALLN, which projects to the dorsal octavolateralis nucleus (DON). The purpose of this study is to examine the response characteristics of ALLN fibers and DON neurons to weak D.C. and sinusoidal electric field stimuli presented as local dipole fields. 2. ALLN fibers respond to presentation of D.C. fields with a phasic burst, followed by a more slowly adapting period of firing. Ascending efferent neurons (AENs) in the DON respond to stimuli with a similar initial burst, which adapts more quickly. 3. Type 1, 2, and 3 neurons are possible local interneurons or commissural DON neurons. Type 1 neurons demonstrate response properties similar to those of AENs. Type 2 cells demonstrated slowly adapting responses to excitatory stimuli, the duration of the response increased with the amplitude of the stimulus. Type 3 neurons demonstrated an increased rate of firing, but the response lacked any specific temporal characteristics. 4. ALLN fibers typically have receptive fields consisting of a single ampulla. The receptive field sizes of DON neurons exhibited varying degrees of convergence for different cell types. 5. Responses of ALLN fibers and DON neurons to weak sinusoidal stimuli demonstrated very similar frequency response characteristics for all cell types. The peak sensitivity of electrosensory neurons was between 5-10 Hz.     

The timing of activity in motor neurons that produce radula movements distinguishes ingestion from rejection in Aplysia

1. We have studied the neural circuitry mediating ingestion and rejection in Aplysia using a reduced preparation that produces ingestion-like and rejection-like motor patterns in response to physiological stimuli.
2. We have characterized 3 buccal ganglion motor neurons that produce specific movements of the radula and buccal mass. B8a and B8b act to close the radula. B10 acts to close the jaws and retract the radula.
3. The patterns of activity in these neurons can be used to distinguish the ingestion-like and rejection-like motor patterns. B8a, B8b and B10 are active together during the ingestion-like pattern. Activity in B8a and B8b ends prior to the onset of activity in B10 during the rejection-like pattern.
4. Our data suggest that these neurons undergo similar patterns of activity in vivo. During both feeding-like patterns, the activity and peripheral actions of B8a, B8b, and B10 are consistent with radula movements observed during ingestion and rejection. In addition, the extracellular activity produced by these neurons is consistent with neural activity observed in vivo during ingestion and rejection.
5. Our data suggest that the different activity patterns observed in these motor neurons contribute to the different radula movements that distinguish ingestion from rejection.

     

A role for GABAergic inhibition in electrosensory processing and common mode rejection in the dorsal nucleus of the little skate, Raja erinacea

The electrosensory primary afferents in elasmobranchs are responsive to electric potentials created by the animal's own ventilation, while the second-order neurons (AENs) which receive this afferent input in the medulla suppress responses to ventilatory potentials but retain their extreme sensitivity to electric signals in the environment. Ventilatory potentials are common mode signals in elasmobranchs and a common mode rejection mechanism is one way the AENs suppress ventilatory noise. By pressure injecting the GABA-A receptor antagonist SR95531 while extracellularly recording from AENs, we tested the hypothesis that the subtractive circuitry that selectively reduces common mode signals in AENs utilizes GABA, and that a GAB-Aergic component of the dorsal nucleus commissural pathway mediates crossed inhibition of AENs. Local application of SR95531 increased the spontaneous activity and the responsiveness of AENs to electrosensory stimuli. AEN responses to a common mode stimulus were selectively increased compared to responses to a localized stimulus due to SR95531 application. Contralateral inhibition of AENs was blocked by SR95531, indicating that GABAergic commissural cells may inhibit AENs when the contralateral side of the body is stimulated, as with common mode stimulation. We conclude that GABAergic inhibition contributes significantly to the shaping of AEN responses including common mode rejection.Abbreviations AENs ascending efferent neurons - GABA gamma-aminobutyric acid     

Discrimination of phase spectra in complex sounds by the bullfrog (Rana catesbeiana)

1. Male bullfrogs at two different natural calling sites were presented with playbacks of synthetic advertisement calls differing in phase spectra. Sounds were presented in a ABA design to analyze the ability of the animals to perceive changes in repeated series of stimuli.
2. The number of individual croaks in an answering call significantly increased over repeated presentations of two of the three stimulus phase types in condition A1. There were significantly fewer croaks to the third stimulus. These data suggest that two stimuli were perceived in a similar manner.
3. Latency of calling to stimuli presented in conditions A and B changed in response to shifts in phase spectrum at a low density calling site. These differences were significant when comparing latency to playbacks where shifts in the phase spectrum changed the temporal fine-structure and waveform periodicity of the stimulus.
4. The increase in number of croaks and decrease in response latency across condition A1 and the increase in latency in condition B suggest that discrimination may take the form of stimulus-specific sensitization. In this context, sensitization might reflect an increase in arousal due to repeated presentation of a salient stimulus.
5. The operation of a hypothetical ‘mating call detector,’ based on linear summation of temporal responses from the eighth nerve, provides output similar to the behavioral results.

     

Independently evolved jamming avoidance responses employ identical computational algorithms: a behavioral study of the African electric fish,Gymnarchus niloticus

An African electric fish, Gymnarchus, and a South American electric fish, Eigenmannia, are believed to have evolved their electrosensory systems independently. Both fishes, nevertheless, gradually shift the frequency of electric organ discharge away when they encounter a neighbor of a similar discharge frequency. Computational algorithms employed by Gymnarchus for this jamming avoidance response have been identified in this study for comparison with those of extensively studied Eigenmannia.

1. Gymnarchus determines whether it should raise or lower its discharge frequency based solely upon the signal mixture of its own reafferent and the exafferent signal from a neighbor, and does not internally refer to the pacemaker command signal which drives its own discharge.
2. The signal mixture is analyzed in terms of the time courses of amplitude modulation and phase modulation at each area of the body surface.
3. Phase of the signal mixture at each area is compared with that of another area for the detection of phase modulation.
4. Unambiguous information necessary for the jamming avoidance response is extracted by integrating information from all body areas each of which yields ambiguous information.
5. These computational features are identical to those of Eigenmannia, suggesting that the neural circuit for jamming avoidance responses may have evolved from preexisting mechanisms for electrolocation in both fishes.

     

A study on the rate of water transport of the clam katelysia opima in relation to environmental conditions

1. The neutral red technique was employed to study the rate of filtration in Katelysia opima.
2. The weight specific water filtration was found to be greater for younger clams compared to the older ones.
3. The rate of water filtration increased with decreasing salinity.
4. Water filtration was found to increase as temperature increased, reaching a maximum at 35°C. but then sharply decreasing at 39°C.
5. Light had no significant effect on the rate of filtration.
6. Suspended matter was found to affect the rate of water filtration.
7. The rate of filtration was low at high pH and high in low pH.
8. The rate of water filtration was found to be faster during high tide than during low tide.
9. The presence of the parasitic crab, Pennotheris sp., in the mantle cavity of clams had a marked effect on the particle filtration.
10. Accidental cut of the siphon tips had no effect on the rate of filtration.

     

Effects of scaphognathite nerve stimulation on the acutely deafferented crab ventilatory central pattern generator

1. Sensory axons from crab (Carcinus maenas) scaphognathites enter the thoracic ganglion primarily via the LNb branch of the levator nerve. The LNa branch of the levator nerve and the depressor nerve each contain relatively few sensory axons.
2. Acutely deafferented ventilatory central pattern generators show a free running burst rate which is lower than that observed in intact crabs. Electrical stimulation of the levator nerve, or of its LNb branch, increases the burst rate in a frequency dependent manner. Stimulation at high enough intensity to recruit afferents will restart a paused motor rhythm. Stimulation of the levator nerve with short pulse trains phase resets and can entrain the rhythm.
3. In addition to increasing the burst rate, LNb stimulation also causes a progressive elimination of motor neurons from the bursts as the stimulating frequency increases, probably due to depolarization of the 3 oval organ ‘giant’ afferent axons in this branch. Intracellular depolarization of single oval organ afferents will also inhibit some motor neurons as well as slow or stop the rhythm.
4. Continuous stimulation of the depressor nerve does not affect the ganglionic burst rate and this nerve contains only a few small diameter afferent axons; however, brief trains of stimuli can reset the rhythm in a phase-dependent manner.

     

Two kinds of peripheral afferent neurons in the earthworm reflex arc

• 1.1. Two kinds of neurons were identified in the body-wall longitudinal muscle layer of the earthworm, Amynthas hawayanus, by the simultaneous potential recording and Lucifer Yellow-CH injection method with a single microelectrode.
• 2.2. Both kinds of neurons have their somata, neuntes and longitudinal processes imbedded in the longitudinal muscle layer. Those with two circular processes extending into the third segmental nerve trunk are tentatively named “intra-nerve-trunk” neurons and those with four circular processes extending into four setae shafts are tentatively named “intramural” neurons.
• 3.3. Both kinds of neurons responded to electrical and mechanical stimuli applied in an afferent direction to them.
• 4.4. The “intra-nerve-trunk” neuron decreased its response amplitudes to these stimuli after the third nerve trunk was sectioned in correlation to the response amplitude decrease recorded from the nerve trunk after it was sectioned.
• 5.5. The response amplitude decrease due to denervation implies a nonlinear structure of the earthworm reflex circuits.
• 6.6. The “intramural” neurons are believed to be primary sensory neurons connected to the mechanoreceptors in the setae.

     

Seasonal variation in the biochemical composition of Mytilus viridis at Ratnagiri on the West Coast of India

1. The seasonal variation in the water, protein, fat and glycogen contents of the mussel, Mytilus viridis has been studied for the year March, 1974 to March, 1975.
2. The water level increased during the monsoon season and decreased in summer.
3. The level of protein, fat and glycogen showed correlation with the reproductive cycle of the mussel.
4. The protein level was high when the mussels were mature and dropped during the breeding period.
5. During sex change from male to female in May the protein level remained high whereas during sex change from female to male in October and November it was low.
6. The fat level was high in mature mussels and declined on spawning.
7. The glycogen level was at its peak in immature mussels and low in mature.

     

Differential modulation of chemical and electrical components of mixed synapses in the lobster stomatogastric ganglion

1. Two pairs of neurons in the pyloric network of the spiny lobster, Panulirus interruptus, communicate through mixed graded chemical and rectifying electrical synapses. The anterior burster (AB) chemically inhibits and is electrically coupled to the ventricular dilator (VD); the lateral pyloric (LP) and pyloric (PY) neurons show reciprocal chemical inhibition and electrical coupling. We examined the effects of dopamine (DA), serotonin (5HT) and octopamine (Oct) on these mixed synapses to determine the plasticity possible with opposing modes of synaptic interaction.
2. Dopamine increased net inhibition at all three pyloric mixed synapses by both reducing electrical coupling and increasing chemical inhibition. This reversed the sign of the net synaptic interaction when electrotonic coupling dominated some mixed synapses, and activated silent chemical components of other mixed synapses.
3. Serofonin weakly enhanced LP → PY net inhibition, by reducing electrical coupling without altering chemical inhibition. Serotonin reduced AB→ VD electrical coupling, but variability in its effect on the chemical component made the net effect non-significant.
4. Octopamine enhanced LP→ PY and PY→ LP net inhibition by enhancing the chemical inhibitory component without altering electrical coupling.
5. Differential modulation of chemical and electrical components of mixed synapses markedly changes the net synaptic interactions. This contributes to the flexible outputs that modulators evoke from anatomically defined neural networks.

     

Colour preferences of flower-naive honeybees

Flower-naive honeybees Apis mellifera L. flying in an enclosure were tested for their colour preferences. Bees were rewarded once on an achromatic (grey, aluminium or hardboard), or on a chromatic (ultraviolet) disk. Since naive bees never alighted on colour stimuli alone, a scent was given in combination with colour. Their landings on twelve colour stimuli were recorded. Results after one reward (“first test”) were analysed separately from those obtained after few rewards (“late tests”).

1. After pre-training to achromatic signals, bees preferred, in the first test, bee-uv-blue and bee-green colours. With increasing experience, the original preference pattern persisted but the choice of bee-blue and bee-green colours increased.
2. Neither colour distance of the test stimuli to the background or to the pre-training signal, nor their intensity, nor their green contrast, accounted for the colour choice of bees. Choices reflected innate preferences and were only associated with stimulus hue.
3. Bees learned very quickly the pre-trained chromatic stimulus, the original colour preferences being thus erased.
4. Colour preferences were strongly correlated with flower colour and its associated nectar reward, as measured in 154 flower species.
5. Colour preferences also resemble the wavelength dependence of colour learning demonstrated in experienced bees.